Hydrolytically susceptible soft segments

Degradable polyurethanes designed with hydrolytically susceptible soft segments... 

The sensitivity to hydrolysis is a key issue in many applications. The ester bond in 4GT-PTMO copolymers is sensitive to hydrolysis however, it is fairly protected since most of the ester is contained in a crystalline structure. The addition of a small amount (1-2%) of a hindered aromatic polycarbodiimide substantially increases the lifetime of this material in the presence of hot water or steam (Brown et al., 1974). Polyurethanes are susceptible to hydrolytic attack, especially those with polyester soft segments. However, polyester soft segment polyurethanes are generally more resistant to oils, organic solvents, and thermal degradation. lonomers will swell when exposed to water in fact, a commercial hydrated perfluorosulfonic ionomer (Nation) is used as a membrane separator in chlor-alkali cells. Styrene-diene copolymers and polyolefin TPEs are insensitive to water. 

Several smdies demonstrated that, despite the hydrolytic stabihty of polyether soft segments, they are susceptible to oxidative degradation and consequently undergo environmental stress cracking (Christenson et al., 2004a,b). 

It has been shown that PURs with hydrophilic soft segments are more susceptible to hydrolytic degradation due to facilitated water uptake. Moreover, more crystalline polymers and polymers prepared with higher molecular weight biostable macrodiols have lower degradation rates (Chemg et al., 2013). 

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