Photodegradable Polycaprolactone Fumarate Block Copolymers

Abstract

A polycaprolactone fumarate copolymer useful as a material for a biocompatible scaffold for tissue engineering applications is disclosed. The copolymer includes at least one caprolactone unit, at least one fumarate unit, and at least one third unit selected from the group consisting of acrylate units and styrenic units. A linking moiety forms a link between the third unit and at least one caprolactone unit or at least one fumarate unit. The linking moiety can be photodegradable. In one form, the third unit includes at least one methyl methacrylate unit. The copolymer can be used to form the wall of a nerve conduit.

What is claimed is: 
     
         1 . A method for forming a nanoporous structure, the method comprising:
 (a) preparing a copolymer comprising (i) at least one caprolactone unit, (ii) at least one fumarate unit, (iii) at least one third unit selected from the group consisting of acrylate units and styrenic units, and (iv) a linking moiety that forms a link between the third unit and at least one caprolactone unit or at least one fumarate unit; and   (b) exposing the linking moiety to photons thereby breaking the link and forming the nanoporous structure.   
     
     
         2 . The method of  claim 1  wherein:
 the nanoporous structure includes pores having a size in a range from 1 to 500 nanometers. 
 
     
     
         3 . The method of  claim 1  wherein:
 the nanoporous structure includes pores having a size in a range from 10 to 100 nanometers. 
 
     
     
         4 . The method of  claim 1  wherein:
 the nanoporous structure has a porosity in a range of about 10% to about 50%. 
 
     
     
         5 . The method of  claim 1  wherein:
 the nanoporous structure has a porosity in a range of about 20% to about 40%. 
 
     
     
         6 . The method of  claim 1  wherein:
 at least one caprolactone unit and at least one fumarate unit form a main chain of the copolymer, and 
 at least one third unit forms a side chain of the copolymer. 
 
     
     
         7 . The method of  claim 1  wherein:
 the third unit is selected from the group consisting of methyl methacrylate units. 
 
     
     
         8 . The method of  claim 1  wherein:
 the copolymer includes a first block in the main chain, the first block having at least one caprolactone unit or at least one fumarate unit, and 
 the copolymer includes a second block in the main chain, the second block having at least one caprolactone unit or at least one fumarate unit, and 
 the linking moiety links the first block and the second block. 
 
     
     
         9 . The method of  claim 1  wherein:
 the linking moiety comprises an alkanoyl group or an alkanedioyl group. 
 
     
     
         10 . The method of  claim 1  wherein:
 the linking moiety comprises a dioxyalkyl group that links the first block and the second block. 
 
     
     
         11 . The method of  claim 1  wherein:
 the linking moiety comprises a trivalent radical of a [(halo-alkylalkanoyl)oxy]-nitrobenzyl dihydroxyalkyl alkanedioate. 
 
     
     
         12 . The method of  claim 1  wherein:
 the copolymer comprises a polycaprolactone fumarate block and a poly(methyl methacrylate) block linked via a covalent bond. 
 
     
     
         13 . The method of  claim 12  wherein:
 the method comprises exposing the copolymer to ultraviolet light thereby breaking the covalent bond. 
 
     
     
         14 . The method of  claim 13  wherein:
 exposing the copolymer to ultraviolet light does not degrade the polycaprolactone fumarate block. 
 
     
     
         15 . The method of  claim 13  wherein:
 breaking the covalent bond allows for selective removal of the poly(methyl methacrylate) block. 
 
     
     
         16 . The method of  claim 12  wherein:
 the copolymer assembles into an ordered nanomaterial. 
 
     
     
         17 . A copolymer comprising:
 at least one caprolactone unit;   at least one fumarate unit; and   a linking moiety that links (i) at least one caprolactone unit and at least one fumarate unit, or (ii) at least one caprolactone unit and at least one caprolactone unit, or (iii) at least one fumarate unit and at least one fumarate unit,   wherein the linking moiety comprises a carboxylic acid group.   
     
     
         18 . The copolymer of  claim 17  wherein:
 the linking moiety is a bivalent radical of a dihydroxyalkyl ester of alkane-dicarboxylic acid. 
 
     
     
         19 . A photodegradable initiator comprising:
 a [(halo-alkylalkanoyl)oxy]-nitrobenzyl dihydroxyalkyl alkanedioate.   
     
     
         20 . The photodegradable initiator of  claim 19  wherein:
 the [(halo-alkylalkanoyl)oxy]-nitrobenzyl dihydroxyalkyl alkanedioate is (5-[(2-bromo-2-methylpropanoyl)oxy]-2-nitrobenzyl dihydroxypropyl butanedioate).