N-alkoxy-4,4-dioxy-polyalkyl-piperidine compounds, their corresponding n-oxides and controlled radical polymerization therewith

Abstract

The present invention relates to selected 1-alkoxy-2,2,6,6 tetramethyl piperidine, 1-alkoxy-2,2 diethyl-6,6 dimethyl piperidine and 1-alkoxy-2,6 diethyl-2,3,6 dimethyl piperidine derivatives which are substituted in the 4 position by two oxygen atoms forming an open chain or cyclic ketal structure, a polymerizable composition comprising a) at least one ethylenically unsaturated monomer and b) said piperidine derivatives. Further aspects of the present invention are a process for polymerizing ethylenically unsaturated monomers, and the use of 1-alkoxy-2,2,6,6 tetramethyl piperidine, 1-alkoxy-2,2 diethyl-6,6 dimethyl piperidine and 1-alkoxy-2,6 diethyl-2,3,6 dimethyl piperidine derivatives which are substituted in the 4 position by two oxygen atoms forming an open chain or cyclic ketal structure for controlled polymerization. The intermediate N-oxyl derivatives, a composition of the N-oxyl derivatives with ethylenically unsaturated monomers and a free radical initiator, as well as a porcess for polymerization are also subjects of the present invention.

1 . A polymerizable composition, comprising 
 a) at least one ethylenically unsaturated monomer or oligomer, and    b) a compound of formula Ia, IIa or IIIa                           wherein 
 n is 1 or 2;  
 X is selected from the group consisting of —CH 2 -phenyl, CH 3 CH-phenyl, (CH 3 ) 2 C-phenyl, (C 5 -C 6 cycloalkyl) 2 CCN, (CH 3 ) 2 CCN, —CH 2 CH═CH 2 , CH 3 CH—CH═CH 2 , 3-cyclohexenyl, 3-cyclopentenyl, (C 1 -C 4 alkyl)CR 20 —C(O)-phenyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—(C 1 -C 4 )alkoxy, (C 1 -C 4 )alkyl-CR 20 —C(O)—(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—N-di(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—NH(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—NH 2 , and a group of formula  
                     
  wherein R 20  is hydrogen or (C 1 -C 4 )alkyl, R 21  is hydrogen, C 1 -C 4 alkyl or phenyl and R 22  is C 1 -C 12 alkyl which is unsubstituted or substituted by OH or N(R 20 )(R 21 ) or which is interrupted by O or NR 20 ;  
 if n is 1 
 Y and Y′ are independently C 1 -C 12 alkyl, C 3 -C 12 alkenyl, C 3 -C 12 alkinyl, C 5 -C 8 cycloalkyl, phenyl, naphthyl, C 7 -C 9 phenylalkyl; or  
 Y and Y′ together form one of the bivalent groups —C(R 1 )(R 2 )—CH(R 3 )—, CH(R 1 )—CH 2 —C(R 2 )(R 3 )—, —CH(R 2 )—CH 2 —C(R 1 )(R 3 )—, —CH 2 —C(R 1 )(R 2 )—CH(R 3 )—, o-phenylene, 1,2-cyclohexyliden,  
 —CH 2 —CH═CH—CH 2 — or  
                     
  wherein 
 R 1  is hydrogen, C 1 -C 12 alkyl, COOH, COO—(C 1 -C 12 )alkyl or CH 2 OR 4 ;  
 R 2  and R 3  are independently hydrogen, methyl ethyl, COOH or COO—(C 1 -C 12 )alkyl;  
 R 4  is hydrogen, C 1 -C 12 alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 18 carbon atoms;  
 
 
 if n is 2 
 Y and Y′ together form one of the tetravalent groups  
                     
 Q is a bisacyl residue which is derived from a C 2 -C 12 dicarboxylic acid or C 1 -C 12 alkylene; and  
 Z is C 1 -C 12 alkylene.  
 
   
     
     
         2 . A polymerizable composition according to  claim 1  wherein the compound is of formula Ia or IIa.  
     
     
         3 . A polymerizable composition according to  claim 1   wherein in the compound of formula Ia, IIa or IIIa 
 X is selected from the group consisting of —CH 2 -phenyl, CH 3 CH-ph nyl, (CH 3 ) 2 C-phenyl, (C 5 -C 6 cycloalkyl) 2 CCN, (CH 3 ) 2 CCN, 3-cyclohexenyl and the other substituents are as defined in  claim 1 .  
   
     
     
         4 . A polymerizable composition according to  claim 1   wherein in the compound of formula Ia, IIa or IIIa X is CH 3 CH-phenyl and the other substituents are as defined in  claim 1 .    
     
     
         5 . A polymerizable composition according to  claim 1   wherein in the compound of formula Ia, IIa or IIIa 
 X is selected from the group consisting of —CH 2 -phenyl, CH 3 CH-phenyl, (CH 3 ) 2 C-phenyl, (C 5 -C 6 cycloalkyl) 2 CCN, (CH 3 ) 2 CCN, 3-cyclohexenyl,  
 n is 1  
 Y and Y′ are independently C 1 -C 12 alkyl, C 3 -C 12 alkenyl, C 3 -C 12 alkinyl, C 5 -C 8 cycloalkyl, phenyl, naphthyl, C 7 -C 9 phenylalkyl; or  
 Y and Y′ together form one of the bivalent groups —C(R 1 )(R 2 )—CH(R 3 )—, CH(R 1 )—CH 2 —C(R 2 )(R 3 )—, —CH(R 2 )—CH 2 —C(R 1 )(R 3 )—, —CH 2 —C(R 1 )(R 2 )—CH(R 3 )—, o-phenylene, 1,2-cyclohexyliden,  
 —CH 2 —CH═CH—CH 2 — or  
                     
  wherein 
 R 1  is hydrogen, C 1 -C 12 alkyl, COOH, COO—(C 1 -C 12 )alkyl or CH 2 OR 4 ;  
 R 2  and R 3  are independently hydrogen, methyl ethyl, COOH or COO—(C 1 -C 12 )alkyl;  
 R 4  is hydrogen, C 1 -C 12 alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 18 carbon atoms.  
 
   
     
     
         6 . A polymerizable composition according to  claim 5   wherein in the compound of formula Ia, IIa or IIIa 
 X is CH 3 CH-phenyl;  
 n is 1  
 Y and Y′ are independently C 1 -C 12 alkyl, C 3 -C 12 alkenyl, phenyl or benzyl; or  
 Y and Y′ together form one of the bivalent groups —C(R 1 )(R 2 )—CH(R 3 )—, CH(R 1 )—CH 2 —C(R 2 )(R 3 )—, —CH(R 2 )—CH 2 —C(R 1 )(R 3 )—, —CH 2 —C(R 1 )(R 2 )—CH(R 3 )—, —CH 2 —CH═CH—CH 2 — wherein 
 R 1  is hydrogen, C 1 -C 12 alkyl, COO—(C 1 -C 12 )alkyl or CH 2 OR 4 ;  
 R 2  and R 3  are independently hydrogen, methyl ethyl, or COO—(C 1 -C 12 )alkyl;  
 R 4  is hydrogen, C 1 -C 12 alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 12 carbon atoms.  
 
   
     
     
         6 . A polymerizable composition according to  claim 1  wherein the compound of formula Ia or IIa is 
 1.) 2,6-Diethyl-4,4-dimethoxy-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine  
 2.) 4,4-Diethoxy-2,6-diethyl-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine  
 3.) 2,6-Diethyl-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-4,4dipropoxy-piperidine  
 4.) 4,4-Dibutoxy-2,6-diethyl-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine  
 5.) 2,6-Diethyl-4,4-diisobutoxy-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine  
 6.) 2,6-Diethyl-2,3,6-trimethyl-4,4-bis-octyloxy-1-(1-phenyl-ethoxy)-piperidine  
 7.) 4,4-Bis-allyloxy-2,6-diethyl-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine  
 8.) 4,4Bis-cyclohexyloxy-2,6-diethyl-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine  
 9.) 4,4-Bis-benzyloxy-2,6diethyl-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine  
 10.) 7,9-Diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 11.) 7,9-Diethyl-2,6,7,9-tetramethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 12.) 2,7,9-Triethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 13.) 7,9-Diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-2-propyl-1,4-dioxa-8-aza-spiro-[4.5]decane  
 14.) 2-Butyl-7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 15.) 7,9-Diethyl-6,7,9-trimethyl-2-octyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decan  
 16.) 2-Decyl-7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 17.) 2-Dodecyl-7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro-[4.5]decane  
 18.) [7,9-Diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2yl-]-methanol  
 19.) Acetic acid 7,9-diethyl-8-hydroxy-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester; compound with isopropyl-benzene  
 20.) Octadecanoic acid 7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester  
 21.) Benzoic acid 7,9-diethyl-8-hydroxy-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ster; compound with isopropyl-benzene  
 22.) 7,9-Diethyl-2-methoxymethyl-6,7,9-trimethyl-8-(1-ph nyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 23.) 2-Cyclohexyloxymethyl-7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4dioxa-8-aza-spiro[4.5]decane  
 24.) 2-Benzyloxymethyl-7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 25.) Octanedioic acid bis-[7,9diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,dioxa-8-aza-spiro[4.5]dec-2-ylmethyl] ester  
 26.) Terephthalic acid bis-[7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl] ester  
 27.) 1,4-Bis-{[7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-yl]-methyloxy}-butane  
 28.) 7,9-Diethyl-2,2,6,7,9-pentamethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 29.) 7,9-Diethyl-2,3,6,7,9-pentamethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 30.) 2,3-Benzo-7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 31.) 2,3-Cyclohexano-7,9-diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 32.) 7,9-Diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane-2,3-dicarboxylic acid  
 33.) 7,9-Diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane-2,3-dicarboxylic acid dimethyl ester  
 34.) 8,10-Diethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 35.) 8,10-Diethyl-3,3,7,8,10-pentamethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro-[5.5]undecane  
 36.) 3,8,10-Triethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 37.) 3,3,8,10-Tetraethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro-[5.5]undecane  
 38.) 8,10-Diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-3-propyl-1,5-dioxa-9-aza-spiro-[5.5]undecane  
 39.) 3-Butyl-3,8,10-triethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro-[5.5]undecane  
 40.) 2,4-Diethyl-1,2,4-trimethyl-3-(1-phenyl-ethoxy)-7,16-dioxa-3aza-dispiro[5.2.5.2]-hexadec-11-ene  
 41.) [8,10-Diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-yl]-methanol  
 42.) [3,8,10-Triethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-yl]-methanol  
 43.) 8,10-Diethyl-3-methoxymethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 44.) 3-Cyclohexyloxymethyl-8,10-diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 45.) 3-Benzyloxymethyl-8,10-diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 46.) Acetic acid 8,10-diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-ylmethyl ester  
 47.) Octanedioic acid bis-[8,10-diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-ylmethyl] ester  
 48.) 1,6-Bis-{3,8,10-triethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-methyloxy}-hexane  
 49.) 8,10-Diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]-undecane-3-carboxylic acid  
 50.) 8,10-Diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]-undecane-3-carboxylic acid methyl ester  
 51.) 8,10-Diethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane-3,3-dicarboxylic acid diethyl ester  
 52.) 3,3-Bisspiro-{8,10-diethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane} 
 53.) 2,4-Diethyl-1,2,4-trimethyl-3-(1-phenyl-ethoxy)-7,12-dioxa-3-aza-spiro[5.6]dodec-9-en  
 54.) 2,2-Diethyl-4,4-dimethoxy-6,6-dimethyl-1-(1-phenyl-ethoxy)-piperidine  
 55.) 4,4-Diethoxy-2,2-diethyl-6,6-dimethyl-1-(1-phenyl-ethoxy)-piperidine  
 56.) 2,2-Diethyl-6,6-dimethyl-1-(1-phenyl-ethoxy)4,4-dipropoxy-piperidine  
 57.) 4,4-Dibutoxy-2,2-diethyl-6,6-dimethyl-1-(1-phenyl-ethoxy)-piperidine  
 58.) 2,2-Diethyl-4,4-diisobutoxy-6,6-dimethyl-1-(1-phenyl-ethoxy)-piperidine  
 59.) 2,2-Diethyl-6,6-dimethyl-4,4-bis-octyloxy-1-(1-phenyl- thoxy)-pip ridine  
 60.) 4,4-Bis-allyloxy-2,2-diethyl-6,6-dimethyl-1-(1-phenyl-ethoxy)-piperidine  
 61.) 4,4-Bis-cyclohexyloxy-2,2-diethyl-6,6-dimethyl-1-(1-phenyl-ethoxy)-piperidine  
 62.) 4,4-Bis-benzyloxy-2,2diethyl-6,6-dimethyl-1-(1-phenyl-thoxy)-piperidine  
 63.) 7,7-Diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 64.) 7,7-Diethyl-2,9,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 65.) 2,7,7-Triethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 66.) 7,7-Diethyl-9,9dimethyl-8-(1-phenyl-ethoxy)-2-propyl-1,4-dioxa-8-aza-spiro[4.5]decane  
 67.) 2-Butyl-7,7-diethyl-9,9dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 68.) 7,7-Diethyl-9,9-dimethyl-2-octyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.51]decane  
 69.) 2-Decyl-7,7-diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 70.) 2-Dodecyl-7,7-diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 71.) [7,7-Diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-yl]-methanol  
 72.) Acetic acid 7,7-diethyl-8-hydroxy-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester; compound with isopropyl-benzene  
 73.) Octadecanoic acid 7,7-diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester  
 74.) Benzoic acid 7,7-diethyl-8-hydroxy-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester; compound with isopropyl-benzene  
 75.) 7,7-Diethyl-2-methoxymethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro-[4.5]decane  
 76.) 2-Cyclohexyloxymethyl-7,7diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 77.) 2-Benzyloxymethyl-7,7-diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro-[4.5]decane  
 78.) Octanedioic acid bis-[7,7-diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro-[4.5]dec-2-ylmethyl] ester  
 79.) Terephthalic acid bis-[7,7-diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl] ester  
 80.) 1,4-Bis-{[7,7-Diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-yl]-methyloxy}-butane  
 81.) 7,7-Diethyl-2,2,9,9-tetramethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]d cane  
 82.) 7,7-Di thyl-2,3,9,9-tetramethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decan  
 83.) 2,3-Benzo-7,7-diethyl-9,9-dim thyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 84.) 2,3-Cyclohexano-7,7-diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane  
 85.) 7,7-Diethyl-9,9dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane-2,3-dicarboxylic acid  
 86.) 7,7-Diethyl-9,9-dimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane-2,3-dicarboxylic acid dimethyl ester  
 87.) 8,8-Diethyl-10,10-dimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 88.) 8,8-Diethyl-3,3,10,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5dioxa-9-aza-spiro[5.5]-undecane  
 89.) 3,8,8-Triethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 90.) 3,3,8,8-Tetraethyl-10,10-dimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]-undecane  
 91.) 8,8-Diethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-3-propyl-1,5-dioxa-9-aza-spiro[5.5]undecane  
 92.) 3-Butyl-3,8,8-triethyl-10,10-dimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]-undecane  
 93.) 2,2-Diethyl-4,4-dimethyl-3-(1-phenyl-ethoxy)-7,16-dioxa-3-aza-dispiro[5.2.5.2]hexadec-11-ene  
 94.) [8,8-Diethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-yl]-methanol  
 95.) [3,8,8-Triethyl-10,10-dimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-yl]-methanol  
 96.) 8,8-Diethyl-3-methoxymethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 97.) 3-Cyclohexyloxymethyl-8,8-diethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 98.) 3-Benzyloxymethyl-8,8-diethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane  
 99.) Acetic acid 8,8-diethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]-undec-3-ylmethyl ster  
 100.) Octanedioic acid bis-[8,8diethyl-3,10,10-trimethyl-9-(1-phenyl- thoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-ylmethyl] ester  
 101.) 1,6-Bis{[3,8,8-triethyl-10,10-dimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-yl]-methyloxy}-hexane  
 102.) 8,8-Diethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane-3-carboxylic acid  
 103.) 8,8-Diethyl-3,10,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane-3-carboxylic acid methyl ester  
 104.) 8,8-Diethyl-10,10dimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane-3,3dicarboxylic acid diethyl ester  
 105.) 3,3-Bisspiro{8,8-diethyl-10,10-dimethyl-9-(1-phenyl-ethoxy)-1,5dioxa-9-aza-spiro[5.5]undecane} 
 106.) 2,2-Diethyl-4,4-dimethyl-3-(1-phenyl-ethoxy)-7,12-dioxa-3-aza-spiro[5.6]dodec-9-ene  
 
     
     
         7 . A composition according to  claim 1  wherein the compound of formula Ia or IIa is 
 4,4-Dibutoxy-2,6-diethyl-2,3,6-trimethyl-1-(1-phenyl-ethoxy)-piperidine;  
 7,9-Diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane;  
 7,9-Diethyl-2,6,7,9-tetramethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]decane;  
 [7,9-Diethyl-6,7,9-trimethyl-8-(1-phenyl-ethoxy)-1,4-dioxa-8-aza-spiro[4.5]dec-2-yl]-methanol;  
 8,10-Diethyl-7,8,10-trimethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane;  
 8,10-Diethyl-3,3,7,8,10-pentamethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undecane;  
 2,4-Diethyl-1,2,4-trimethyl-3-(1-phenyl-ethoxy)-7,16-dioxa-3-aza-dispiro[5.2.5.2]hexadec-11-ene;  
 [8,10-Diethyl-3,7,8,10-tetramethyl-9-(1-phenyl-ethoxy)-1,5-dioxa-9-aza-spiro[5.5]undec-3-yl]-methanol or  
 9-(Cyclohex-2-enyloxy)-8,10-diethyl-3,3,7,8,10-pentamethyl-1,5-dioxa-9-aza-spiro[5.5]undecane.  
 
     
     
         8 . A composition according to  claim 1 , wherein the ethylenically unsaturated monomer or oligomer is selected from the group consisting of ethylene, propylene, n-butylene, i-butylene, styrene, substituted styrene, conjugated dienes, acrolein, vinyl acetate, vinylpyrrolidone, vinylimidazole, maleic anhydride, (alkyl)acrylic acidanhydrides, (alkyl)acrylic acid salts, (alkyl)acrylic esters, (meth)acrylonitriles, (alkyl)acrylamides, vinyl halides or vinylidene halides.  
     
     
         9 . A composition according to  claim 8 , wherein the ethylenically unsaturated monomers are ethylene, propylene, n-butylene, i-butylene, isoprene, 1,3-butadiene, α-C 5 -C 18 alkene, styrene, α-methyl styrene, p-methyl styrene or a compound of formula CH 2 ═C(R a )—(C═Z)—R b , wherein R a  is hydrogen or C 1 -C 4 alkyl, R b  is NH 2 , O − (Me + ), glycidyl, unsubstituted C 1 -C 18 alkoxy, C 2 -C 100 alkoxy interrupted by at least one N and/or O atom, or hydroxy-substituted C 1 -C 18 alkoxy, unsubstituted C 1 -C 18 alkylamino, di(C 1 -C 18 alkyl)amino, hydroxy-substituted C 1 -C 18 alkylamino or hydroxy-substituted di(C 1 -C 18 alkyl)amino, —O—CH 2 —CH 2 —N(CH 3 ) 2  or —O—CH 2 —CH 2 —N + H(CH 3 ) 2  An − ; 
 An −  is a anion of a monovalent organic or inorganic acid;  
 Me is a monovalent metal atom or the ammonium ion.  
 Z is oxygen or sulfur.  
 
     
     
         10 . A composition according to  claim 1 , wherein the compound of formula Ia, IIa or IIIa is present in an amount of from 0.01 mol-% to 20 mol-%,  
     
     
         11 . A process for preparing an oligomer, a cooligomer, a polymer or a copolymer (block or random) by free radical polymerization of at least one ethylenically unsaturated monomer or oligomer, which comprises (co)polymerizing the monomer or monomers/oligomers in the presence of an initiator compound of formula Ia, IIa or IIIa under reaction conditions capable of effecting scission of the O—C bond to form two free radicals, the radical .X being capable of initiating polymerization.  
     
     
         12 . A process according to  claim 11 , wherein the scission of the O—C bond is effected by heating and takes place at a temperature of between 50° C. and 160° C.  
     
     
         13 . A compound of formula Ia, IIa or IIIa  
       
         
           
           
               
               
           
         
       
       wherein 
 n is 1 or 2;  
 X is selected from the group consisting of —CH 2 -phenyl, CH 3 CH-phenyl, (CH 3 ) 2 C-phenyl, (C 5 -C 6 cycloalkyl) 2 CCN, (CH 3 ) 2 CCN, —CH 2 CH═CH 2 , CH 3 CH—CH═CH 2 , 3, cycloh xenyl, 3-cyclo-pentenyl, (C 1 -C 4 alkyl)CR 20 —C(O)-phenyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—(C 1 -C 4 )alkoxy, (C 1 -C 4 )alkyl-CR 20 —C(O)—(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—N-di(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—NH(C 1 -C 4 )alkyl, (C 1 -C 4 )alkyl-CR 20 —C(O)—NH 2 , and a group of formula  
                     
  wherein R 20  is hydrogen or (C 1 -C 4 )alkyl, R 21  is hydrogen, C 1 -C 4 alkyl or phenyl and R 22  is C 1 -C 12 alkyl which is unsubstituted or substituted by OH or N(R 20 )(R 21 ) or which is interrupted by O or NR 20 ;  
 if n is 1 
 Y and Y′ are independently C 1 -C 12 alkyl, C 3 -C 12 alkenyl, C 3 -C 12 alkinyl, C 5 -C 8 -cycloalkyl, phenyl, naphthyl, C 7 -C 9 phenylalkyl; or  
 Y and Y′ together form one of the bivalent groups —C(R 1 )(R 2 )—CH(R 3 )—, CH(R 1 )—CH 2 —C(R 2 )(R 3 )—, —CH(R 2 )—CH 2 —C(R 1 )(R 3 )—, —CH 2 —C(R 1 )(R 2 )—CH(R 3 )—, o-phenylene, 1,2-cyclohexyliden,  
 —CH 2 —CH═CH—CH 2 — or  
                     
  wherein 
 R 1  is hydrogen, C 1 -C 12 alkyl, COOH, COO—(C 1 -C 12 )alkyl or CH 2 OR 4 ;  
 R 2  and R 3  are independently hydrogen, methyl ethyl, COOH or COO—(C 1 -C 12 )alkyl;  
 R 4  is hydrogen, C 1 -C 12 alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 18 carbon atoms;  
 
 
 if n is 2 
 Y and Y′ together form one of the tetravalent groups  
                     
 Q is a bisacyl residue which is derived from a C 2 -C 12 dicarboxylic acid or C 1 -C 12 alkylene; and  
 Z is C 1 -C 12 alkylene; with the proviso that compounds A, B, C are excluded  
                     
 
 
     
     
         14 . A polymerizable composition, comprising 
 a) at least one ethylenically unsaturated monomer or oligomer;    b) a compound of formula Ib or IIb                           wherein 
 n is 1 or 2;  
 if n is 1 
 Y and Y′ are independently C 1 -C 12 alkyl, C 3 -C 12 alkenyl, C 3 -C 12 alkinyl, C 5 -C 8 cycloalkyl, phenyl, naphthyl, C 7 -C 9 phenylalkyl; or  
 Y and Y′ together form one of the bivalent groups —C(R 1 )(R 2 )—CH(R 3 )—, CH(R 1 )—CH 2 —C(R 2 )(R 3 )—,  
 —CH(R 2 )—CH 2 —C(R 1 )(R 3 )—, —CH 2 —C(R 1 )(R 2 )—CH(R 3 )—, o-phenylene, 1,2-cyclohexyliden, —CH 2 —CH═CH—CH 2 — or  
                     
  wherein 
 R 1  is hydrogen, C 1 -C 12 alkyl, COOH, COO—(C 1 -C 12 )alkyl or CH 2 OR 4 ;  
 R 2  and R 3  are independently hydrogen, methyl ethyl, COOH or COO—(C 1 -C 12 )alkyl;  
 R 4  is hydrogen, C 1 -C 12 alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 18 carbon atoms;  
 
 
 if n is 2 
 Y and Y′ together form one of the tetravalent groups  
                     
 Q is a bisacyl residue which is derived from a C 2 -C 12 dicarboxylic acid or C 1 -C 12 alkylene; and  
 Z is C 1 -C 12 alkylene; and  
 c) a source of free radicals capable of initiating polymerization of ethylenically unsaturated monomers.  
 
   
     
     
         15 . A polymerizable composition according to  claim 14   wherein in the compound of formula Ib, IIb or IIIb 
 n is 1  
 Y and Y′ are independently C 1 -C 12 alkyl, C 3 -C 12 alkenyl, phenyl or benzyl; or  
 Y and Y′ together form one of the bivalent groups —C(R 1 )(R 2 )—CH(R 3 )—, CH(R 1 )—CH 2 —C(R 2 )(R 3 )—, —CH(R 2 )—CH 2 —C(R 1 )(R 3 )—, —CH 2 —C(R 1 )(R 2 )—CH(R 3 )—, —CH 2 —CH═CH—CH 2 — or; wherein 
 R 1  is hydrogen, C 1 -C 12 alkyl, COO—(C 1 -C 12 )alkyl or CH 2 OR 4 ;  
 R 2  and R 3  are independently hydrogen, methyl ethyl, or COO—(C 1 -C 12 )alkyl;  
 R 4  is hydrogen, C 1 -C 12 alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 12 carbon atoms.  
 
   
     
     
         16 . A polymerizable composition according to  claim 14  wherein the compound of formula Ib or IIb is 
 1.) 2,6-Diethyl-4,4-dim thoxy-2,3,6-trimethyl-piperidin-1-oxyl  
 2.) 4,4-Diethoxy-2,6-diethyl-2,3,6-trimethyl-piperidin-1-oxyl  
 3.) 2,6-Diethyl-2,3,6-trimethyl-4,4-dipropoxy-piperidin-1-oxyl  
 4.) 4,4-Dibutoxy-2,6-diethyl-2,3,6-trimethyl-piperidin-1-oxyl  
 5.) 2,6-Diethyl-4,4-diisobutoxy-2,3,6-trimethyl-piperidin-1-oxyl  
 6.) 2,6-Diethyl-2,3,6-trimethyl-4,4-bis-octyloxy-piperidin-1-oxyl  
 7.) 4,4-Bis-allyloxy-2,6-diethyl-2,3,6-trimethyl-piperidin-1-oxyl  
 8.) 4,4-Bis-cyclohexyloxy-2,6-diethyl-2,3,6-trimethyl-piperidin-1-oxyl  
 9.) 4,4-Bis-benzyloxy-2,6-diethyl-2,3,6-trimethyl-piperidin-1-oxyl  
 10.) 7,9-Diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 11.) 7,9-Diethyl-2,6,7,9-tetramethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 12.) 2,7,9-Triethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 13.) 7,9-Diethyl-6,7,9-trimethyl-2-propyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 14.) 2-Butyl-7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 15.) 7,9-Diethyl-6,7,9-trimethyl-2-octyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 16.) 2-Decyl-7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 17.) 2-Dodecyl-7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 18.) 7,9-Diethyl-2-hydroxymethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 19.) Acetic acid 7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester-8-oxyl  
 20.) Octadecanoic acid 7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester-8-oxyl  
 21.) Benzoic acid 7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester-8-oxyl  
 22.) 7,9-Diethyl-2-methoxymethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 23.) 2-Cyclohexyloxymethyl-7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 24.) 2-Benzyloxymethyl-7,9-diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 25.) Octanedioic acid bis-(7,9-diethyl-8-oxyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl) ester  
 26.) Terephthalic acid bis-(7,9diethyl-8-oxyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl) ester  
 27.) 1,4-Bis-{[7,9-diethyl-6,7,9-trimethyl-8-oxyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-yl]-methyloxy}-butane  
 28.) 7,9-Diethyl-2,2,6,7,9-pentamethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 29.) 7,9-Diethyl-2,3,6,7,9-pentamethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 30.) 2,3-Benzo-7,9-diethyl-6,7,9-trimethyl-8-oxyl-1,4-dioxa-8-aza-spiro[4.5]decan  
 31.) 2,3-Cyclohexano-7,9-diethyl-6,7,9-trimethyl-8-oxyl-1,4-dioxa-8-aza-spiro[4.5]decane  
 32.) 7,9-Diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decane2,3-dicarboxylic acid-8-oxyl  
 33.) 7,9-Diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decane-2,3-dicarboxylic acid dimethyl ester-8-oxyl  
 34.) 8,10-Diethyl-7,8,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 35.) 8,10-Diethyl-3,3,7,8,10-pentamethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 36.) 3,8,10-Triethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 37.) 3,3,8,10-Tetraethyl-7,8,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 38.) 8,10-Diethyl-3,7,8,10-tetramethyl-3-propyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 39.) 3-Butyl-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 40.) 2,4-Diethyl-1,2,4-trimethyl-7,16-dioxa-3-aza-dispiro[5.2.5.2]hexadec-11-en-3-oxyl  
 41.) 8,10-Diethyl-3-hydroxymethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 42.) 3,8,10-Triethyl-3-hydroxymethyl-7,8,10-trimethyl-1,5dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 43.) 8,10-Diethyl-3-methoxymethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 44.) 3-Cyclohexyloxymethyl-8,10-diethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]-undecan-9-oxyl  
 45.) 3-Benzyloxymethyl-8,10-diethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 46.) Acetic acid 8,10-diethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undec-3-ylmethyl ester-9-oxyl  
 47.) Octanedioic acid bis-(8,10-diethyl-9-oxyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undec-3-ylmethyl) ester  
 48.) 1,6-Bis-{3,8,10-triethyl-7,8,10-trimethyl-9-oxyl-1,5-dioxa-9-azaspiro[5.5]undec-3-methyloxy}-hexane  
 49.) 8,10-Diethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecane-3-carboxylic acid-9-oxyl  
 50.) 8,10-Diethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecane-3-carboxylic acid methyl ester-9-oxyl  
 51.) 8,10-Diethyl-7,8,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-3,3-dicarboxylic acid diethyl ester-9-oxyl  
 52.) 3,3-Bisspiro-{8,10-diethyl-7,8,10-trimethyl-9-oxyl-1,5-dioxa-9-aza-spiro[5.5]undecane} 
 53.) 2,4-Diethyl-1,2,4-trimethyl-7,12-dioxa-3-aza-spiro[5.6]dodec-9-en-3-oxyl  
 54.) 2,2-Diethyl-4,4-dimethoxy-6,6-dimethyl-piperidin-1-oxyl  
 55.) 4,4-Diethoxy-2,2-diethyl-6,6-dimethyl-piperidin-1-oxyl  
 56.) 2,2-Diethyl-6,6-dimethyl-4,4-dipropoxy-piperidin-1-oxyl  
 57.) 4,4-Dibutoxy-2,2-diethyl-6,6-dimethyl-piperidin-1-oxyl  
 58.) 2,2-Diethyl-4,4-diisobutoxy-6,6-dimethyl-piperidin-1-oxyl  
 59.) 2,2-Diethyl-6,6-dimethyl-4,4-bis-octyloxy-piperidin-1-oxyl  
 60.) 4,4-Bis-allyloxy-2,2-diethyl-6,6-dimethyl-piperidin-1-oxyl  
 61.) 4,4-Bis-cyclohexyloxy-2,2-diethyl-6,6-dimethyl-piperidin-1-oxyl  
 62.) 4,4-Bis-benzyloxy-2,2-diethyl-6,6-dimethyl-piperidin-1-oxyl  
 63.) 7,7-Diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 64.) 7,7-Diethyl-2,9,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 65.) 2,7,7-Triethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 66.) 7,7-Diethyl-9,9-dimethyl-2-propyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 67.) 2-Butyl-7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 68.) 7,7-Diethyl-9,9-dimethyl-2-octyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 69.) 2-Decyl-7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 70.) 2-Dodecyl-7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 71.) 7,7-Diethyl-2-hydroxymethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 72.) Acetic acid 7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester-8-oxyl  
 73.) Octadecanoic acid 7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester-8-oxyl  
 74.) Benzoic acid 7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl ester-8-oxyl  
 75.) 7,7-Diethyl-2-methoxymethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 76.) 2-Cyclohexyloxymethyl-7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 77.) 2-Benzyloxymethyl-7,7-diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 78.) Octanedioic add bis-(7,7-diethyl-8-oxyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl) ester  
 79.) Terephthalic acid bis-(7,7-diethyl-8-oxyl-9,9-dim thyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-ylmethyl) ester  
 80.) 1,4-Bis-{[7,7-diethyl-9,9-dimethyl-8-oxyl-1,4-dioxa-8-aza-spiro[4.5]dec-2-yl]-methyloxy}-butane  
 81.) 7,7-Diethyl-2,2,9,9-tetramethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 82.) 7,7-Diethyl-2,3,9,9tetramethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl  
 83.) 2,3-Benzo-7,7-diethyl-9,9-dimethyl-8-oxyl-1,4-dioxa-8-aza-spiro[4.5]decane  
 84.) 2,3-Cyclohexano-7,7diethyl-9,9-dimethyl-8-oxyl-1,4dioxa-8-azaspiro [4.5]decane  
 85.) 7,7-Diethyl-9,9dimethyl-1,4-dioxa-8-aza-spiro[4.5]decane-2,3-dicarboxylic acid-8-oxyl  
 86.) 7,7-Diethyl-9,9-dimethyl-1,4-dioxa-8-aza-spiro[4.5]decane-2,3-dicarboxylic acid dimethyl ester-8-oxyl  
 87.) 8,8-Diethyl-10,10-dimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 88.) 8,8-Diethyl-3,3,10,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 89.) 3,8,8-Triethyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 90.) 3,3,8,8-Tetraethyl-10,10-dimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 91.) 8,8-Diethyl-3,10,10-trimethyl-3-propyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 92.) 3-Butyl-3,8,8-triethyl-10,10-dimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 93.) 2,2-Diethyl-4,4-dimethyl-7,16-dioxa-3-aza-dispiro[5.2.5.2]hexadec-11-en-3-oxyl  
 94.) 8,8-Diethyl-3-hydroxymethyl-3,10,10-trimethyl-1,5dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 95.) 3,8,8-Triethyl-3-hydroxymethyl-10,10-dimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 96.) 8,8-Diethyl-3-methoxymethyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 97.) 3-Cyclohexyloxymethyl-8,8-diethyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 98.) 3-Benzyloxymethyl-8,8-diethyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl  
 99.) Acetic acid 8,8-diethyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undec-3-ylmethyl ester-9-oxyl  
 100.) Octanedioic acid bis-(8,8-diethyl-9-oxyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undec-3-ylmethyl) ester  
 101.) 1,6-Bis{[3,8,8-triethyl-10,10-dimethyl-9-oxyl-1,5-dioxa-9-aza-spiro[5.5]undec-3-yl]-methyloxy}-hexane  
 102.) 8,8-Diethyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecane-3-carboxylic acid-9-oxyl  
 103.) 8,8-Diethyl-3,10,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecane-3-carboxylic acid methyl ester-9-oxyl  
 104.) 8,8-Diethyl-10,10-dimethyl-1,5-dioxa-9-aza-spiro[5.5]undecane-3,3-dicarboxylic acid diethyl ester-9-oxyl  
 105.) 3,3-Bisspiro{8,8-diethyl-10,10-dimethyl-9-oxyl-1,5-dioxa-9-aza-spiro[5.5]undecane} 
 106.) 2,2-Diethyl-4,4-dimethyl-7,12-dioxa-3-aza-spiro[5.6]dodec-9-en-3-oxyl  
 
     
     
         17 . A polymerizable composition according to  claim 14  wherein the compound of formula Ib or IIb is 
 4,4-Dibutoxy-2,6-diethyl-2,3,6-trimethyl-piperidin-1-oxyl;  
 7,9-Diethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl;  
 7,9-Diethyl-2,6,7,9-tetramethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl;  
 7,9-Diethyl-2-hydroxymethyl-6,7,9-trimethyl-1,4-dioxa-8-aza-spiro[4.5]decan-8-oxyl;  
 8,10-Diethyl-7,8,10-trimethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxyl;  
 8,10-Diethyl-3,3,7,8,10-pentamethyl-1,5dioxa-9-aza-spiro[5.5]undecan-9-oxyl;  
 2,4-Diethyl-1,2,4-trimethyl-7,16-dioxa-3-aza-dispiro[5.2.5.2]hexadec-11-en-3-oxyl;  
 8,10-Diethyl-3-hydroxymethyl-3,7,8,10-tetramethyl-1,5-dioxa-9-aza-spiro[5.5]undecan-9-oxy  
 
     
     
         18 . A process for preparing an oligomer, a cooligomer, a polymer or a copolymer (block or random) by free radical polymerization of at least one ethylenically unsaturated monomer/oligomer, which comprises subjecting the composition according to  claim 14  to heat or actinic radiation.  
     
     
         19 . A compound of formula Ib or IIb  
       
         
           
           
               
               
           
         
       
       wherein 
 n is 1 or 2;  
 if n is 1 
 Y and Y′ are independ ntly C 1 -C 12 alkyl, C 3 -C 12 alkenyl, C 3 -C 12 alkinyl, C 5 -C 8 cycloalkyl, phenyl, naphthyl, C 7 -C 9 phenylalkyl; or  
 Y and Y′ together form one of th bivalent groups —C(R 1 )(R 2 )—CH(R 3 )—, CH(R 1 )—CH 2 —C(R 2 )(R 3 )—, —CH(R 2 )—CH 2 —C(R 1 )(R 3 )—, —CH 2 —C(R 1 )(R 2 )—CH(R 3 )—, o-phenylene, 1,2-cyclohexyliden,  
 —CH 2 —CH═CH—CH or  
                     
  wherein 
 R 1  is hydrogen, C 1 -C 12 alkyl, COOH, COO—(C 1 -C 12 )alkyl or CH 2 OR 4 ;  
 R 2  and R 3  are independently hydrogen, methyl ethyl, COOH or COO—(C 1 -C 12 )alkyl;  
 R 4  is hydrogen, C 1 -C 12 alkyl, benzyl, or a monovalent acyl residue derived from an aliphatic, cycloaliphatic or aromatic monocarboxylic acid having up to 18 carbon atoms;  
 
 
 if n is 2 
 Y and Y′ together form one of the tetravalent groups  
                     
 Q is a bisacyl residue which is derived from a C 2 -C 12 dicarboxylic acid or C 1 -C 12 alkylene; and  
 Z is C 1 -C 12 alkylene; with the proviso that compounds D, E, F, G, H  
                     
  are excluded.  
 
 
     
     
         20 . A polymer or oligomer, having attached at least one oxyamine group derived from formula Ia, IIa or IIIa according to  claim 1 .  
     
     
         21 . Use of a compound of formulae Ia, IIa or IIIa according to  claim 1  for the polymerization of ethylenically unsaturated monomers.  
     
     
         22 . Use of a compound of formulae Ib or IIb according to  claim 14  for the polymerization of ethylenically unsaturated monomers together with a source of free radicals.