Surface modification of polymer foams using plasma

Abstract

An embodiment includes a system comprising: a monolithic shape memory polymer (SMP) foam having first and second states; wherein the SMP foam includes: (a) polyurethane, (b) an inner half portion having inner reticulated cells defined by inner struts, (c) an outer half portion, having outer reticulated cells defined by outer struts, surrounding the inner portion in a plane that provides a cross-section of the SMP foam, (d) hydroxyl groups chemically bound to outer surfaces of both the inner and outer struts. Other embodiments are discussed herein.

1 . A method comprising:
 locating a monolithic, polyurethane, shape memory polymer (SMP) foam, which has first and second states, in a chamber;   pressuring the chamber to a first pressure level range;   providing a first gas to the chamber while the chamber is at the first pressure level range;   ionizing the first gas into a first plasma; and   exposing the SMP foam to the first plasma for a first period of time to oxidize both inner and outer strut surfaces of the SMP foam and reticulate cells of the SMP foam via plasma reticulation.   
     
     
         2 . The method of  claim 1 , wherein the first gas includes oxygen and tetrafluoromethane. 
     
     
         3 . The method of  claim 2  comprising functionalizing a surface of the SMP foam with hydroxyl groups. 
     
     
         4 . The method of  claim 2  comprising functionalizing a surface of the SMP foam with hydroxyl groups in response to reticulating the SMP foam via plasma reticulation. 
     
     
         5 . The method of  claim 1  comprising functionalizing a surface of the SMP foam with hydroxyl groups in response to reticulating the SMP foam via plasma reticulation. 
     
     
         6 . The method of  claim 1  comprising, after exposing the SMP foam to the first plasma for a first period of time, the following operations:
 pressuring at least one of the chamber or another chamber, which includes the SMP foam, to a second pressure level range; 
 providing a second gas to the at least one of the chamber or another chamber while the at least one of the chamber or another chamber is at the second pressure level range; 
 exposing the SMP foam to the second gas for a second period of time. 
 
     
     
         7 . The method of  claim 6  comprising exposing the SMP foam to the second gas for a second period of time to produce a diffusion barrier on the SMP foam. 
     
     
         8 . The method of  claim 7  comprising:
 ionizing the second gas into a second plasma; and 
 wherein exposing the SMP foam to the second gas for the second period of time includes exposing the SMP foam to the second plasma for the second period of time to produce the diffusion barrier on the SMP foam via plasma enhanced chemical vapor deposition. 
 
     
     
         9 . The method of  claim 7 , wherein the diffusion barrier includes a hydrocarbon film on the inner and outer strut surfaces. 
     
     
         10 . The method of  claim 9 , wherein the hydrocarbon film is no thicker than 500 nm. 
     
     
         11 . The method of  claim 10 , wherein the second gas includes at least one hydrocarbon gas. 
     
     
         12 . The method of  claim 10 , wherein the second gas includes at least one of acetylene, ethylene, propylene, methane, isobutylene, ethane, propane, butane, argon, or combinations thereof. 
     
     
         13 . The method of  claim 7  comprising:
 masking a portion of the SMP foam before exposing the SMP foam to the second gas for the second period of time; 
 wherein in response to masking the portion of the SMP foam, one part of the foam has more diffusion barrier than another part of the foam. 
 
     
     
         14 . The method of  claim 7 , wherein the second pressure level range is between 5 and 250 mTorr. 
     
     
         15 . The method of  claim 14 , wherein the first pressure level range is between 300 and 500 mTorr. 
     
     
         16 . The method of  claim 1  comprising:
 masking a portion of the SMP foam before exposing the SMP foam to the first plasma for the first period of time; 
 wherein in response to masking the portion of the SMP foam, one part of the foam is more reticulated than another part of the foam. 
 
     
     
         17 . The method of  claim 1 , wherein the SMP foam is a reaction product of N,N,N′,N′-tetrakis (2-hydroxypropyl) ethylenediamine (HPED), triethanolamine (TEA), and hexamethylene diisocyanate (HDI). 
     
     
         18 . The method of  claim 1 , wherein the SMP foam is a reaction product of N,N,N′,N′-tetrakis (2-hydroxypropyl) ethylenediamine (HPED), triethanolamine (TEA), and trimethyl hexamethylene diisocyanate (TMHDI). 
     
     
         19 . The method of  claim 1 , wherein the SMP foam is a reaction product of Glycerol and hexamethylene diisocyanate (HDI). 
     
     
         20 . The method of  claim 1 , wherein the SMP foam is a reaction product of Glycerol and at least one of trimethyl hexamethylene diisocyanate (TMHDI), hexamethylene diisocyanate (HDI), or combinations thereof