Molecular design and properties of degradable thermoplastic elastomers
Final Report Abstract
The project focused on providing the synthetic strategies and characterization of new polycaprolactone (PCL) based degradable, thermoplastic elastomers with low elastic modulus and high elongation at break. The phase separated morphology for the formation of degradable thermoplastic elastomers was based on the generation of block copolymers of high molecular weight crystalline and amorphous polycaprolactone (PCL). Crystalline PCL made by ring-opening polymerization (ROP) of ε-caprolactone generated the hard block and amorphous PCL/PCL-copolymers made by radical ring-opening polymerization (RROP) of 2-methylene-1,3-dioxepane (MDO) and copolymers with methyl methacrylate (MMA) created the soft segment. The formation of block copolymers by combination of metal catalysed ROP of caprolactone followed by conversion of polymer chain ends to atom transfer radical polymerization (ATRP) initiator and RROP of MDO was not possible. The growing polymer chain after RROP of MDO had unstable primary radical at the chain end. There was no driving force for the de-capping reaction during ATRP of MDO and therefore could not be polymerized. Therefore, a new methodology was established for making degradable thermoplastic elastomers using conventional radical polymerization by making use of semicrystalline PCL based macro azo initiators for RROP of MDO and MDO-MMA mixture. Many different polymers were made by changing the composition of MMA and MDO and block lengths. The composition and block length of the block copolymers influenced properties like optical, mechanical and thermal.The procedure is simple and up-scalable. Basic studies for the formation of functional degradable polyester amorphous block based on copolymers of cyclic ketene acetals and vinyl monomers like 2-hydroxyethyl methacrylate (HEMA) and dimethylaminoethylmethacrylate (DMAEMA) were also successfully done and many new interesting degradable polymers were generated. Formation of thermoplastic elastomers by making block copolymers using ATRP was not successful. The way out for future work could be the use of PCL based macro azo initiator as shown for other polymers.
Publications
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Synthetic route and characterization of main chain ester containing hydrolytically degradable poly(N, N-dimethylaminoethyl methacrylate) based polycations., Macromol. Chem. Phys. 2010, 211, 905
Seema Agarwal
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Degradable elastomeric block copolymers based on polycaprolactone by freeradical chemistry, Macromol. Chem. Phys. 2011, 212(13), 1327
Seema Agarwal
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Biocompatible and degradable poly(2-hydroxyethyl methacrylate) based polymers for biomedical applications, Polym. Chem., 2012, 3, 2752
Seema Agarwal
