Polylactic acids block copolymers

FIGURE 5 Stepwise synthesis of a triblock copolymer (PCL-PLA-PCL) of PCL and polylactic acid using aluminum coordination catalysts to minimize randomization of the block structure by transesterification. (From Ref. 43.)... 

Block copolymers, (IV), consisting of succinic acid coupled with propylene glycol and then capped with hexamethylene diisocyanate and reacted with polylactic acid were prepared by Imamura [5] and used as biodegradable containers. 

Amphiphilic block copolymers consisting of polylactic acid or poly(lactic acid-h-glycolic acid) terminated with tocopherol or cholesterol were prepared by Seo [1] and used as drug delivery agents for Paclitaxel . 

Self-assembled block copolymers are basically amphilic molecules which contain distinctively different polymers. This block copolymer contains two or more polymers quantitatively in the form of blocks. Some of the block copolymers are polyacrylic acid, polymethylacrylate, polystyrene polyethylene oxide, polybutadiene, polybutylene oxide, poly-2-methyloxazoline, polydimethyl sUoxane, poly-e-caprolactone, polypropylene sulfide, poly-A -isopropylacrylamide, poly-2-vinylpyridine, poly-2-diethylamino ethyl methacrylate, poly-2-(diisopropylamino) ethyl methacrylate, poly-2-(methacryloyloxy) ethyl phosphorylcholine, and polylactic acid. These copolymers contain more than polymers to form certain configurations like linear, branched, patterned. For example, if we take three polymers named A, B, and C, they can be combined to form arrangements AB, BA, AA, BAB, ABCAB, ABCABC, ABABAB, etc. in the form of branched configuration it forms (ABQa, (ABA)a, (AB)4, etc. Depending on the above-mentioned number of blocks, they are named as AB diblock copolymers, ABC triblock copolymers, ABC star block copolymers, etc. The covalent linkage between these different blocks of polymers makes macroscopic phase separation impossible, that is, in its place the phase separation... 

Microthermal analysis has been used in surface and depth profiling studies of PP [51,52], multi-block copolymers [53], polytetrafluoroethylene/silicone blends [14],PEG/polylactic acid blends [55], and PS/polyvinyl methyl ether blends [56]. See also Section 3.12. 

Details are given of the synthesis of biodegradable graft copolymers based on a backbone of polylactic acid grafted with short blocks of polyacrylamide. Emulsion and solution polymerisations were examined. Molecular structures were determined by proton NMR and FTIR and by DSC. Cytotoxicity tests were conducted to assess their biocompatibility. Preliminary results of their potential in controlled release technologies are reported. 17 refs. 

Miyamoto, S., Takaoka, K., Okada, T., Yoshikawa, H., Hashimoto, J., Suzuki, S., and Ono, K. Polylactic acid-polyethylene glycol block copolymer. A new biodegradable synthetic carrier for bone morphogenetic protein. Clin. Orthop. 333-343,1993. 

MTA has been nsed in surface and depth profiling studies on polypropylene (PP) [15, 16], multi-block copolymers [12], PTFE/silicone blends [13], polyethylene glycol (PEG) polylactic acid blends [17], PS-PVME blends [14] and PP [15]. 

Polylactic acid-co-P-ethylene glycol Study of chemical linkages between PEG and PEA segments in block copolymers [88]... 

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