Studies On The Synthesis Of Amphiphilic Block Copolymer PDMAEMA-b-PLA And Its Properties

Biomedical polymers have attracted much attention due to their efficiently loading drugsand controlled drug release. The biomedical polymers are reqired non-toxicicity and excellentbiocompatibility, as well as stimuli-response for drug controlled release. Thus, biocompatiblemonomers were selected as monomers, such as methyl acrylate N,N-dimethylaminoethylmethacrylate (DMAEMA), lactide and4-vinyl-phenylboronic acid (VBA) in this research tosynthsize the copolymers with pH, CO2responsive block copolymer and glucose responsivetri-block copolymer.Multi-responsive block copolymer, poly (dimethylamino-2-ethylmethacrylate)-block-poly (lactide)(PDMAEMA-b-PLA) was synthesized by Ring-openingPolymerization (ROP) and Reversible Addition-Fragmentation Chain TransferPolymerization (RAFT). Firstly, homopolymer PDMAEMA was synthesized by RAFTradical polymerization in the presence of S,S-bis (,,-dimethyl-,-ethylacetate)-trithiocarbonate (TTC-OH) as chain transfer agent. Then, amphiphilic copolymer(PDMAEMA-b-PLA) was prepared by ring opening polymerization (ROP) using thehomopolymer PDMAEMA as initiator. Structures of the homopolymer and block copolymerswere confirmed by FT-IR, GPC and1H-NMR. The block copolymers were self-assembledinto micelles, and their particle sizes and morphologies were investigated by ultravioletspectrophotometer (UV-Vis), Zeta potential and particle size analyzer and Scan ElectronMicroscopy (SEM). Moreover, the sizes and morphologies changing with CO2and pHresponses were also detected. The results showed that the copolymers with different ratiosbetween PLA and PDMAEMA units had different vritical water contents (cwc) and particlesizes. The block copolymeric micelles had pH sensitivity and CO2responsibility, and theresponsibilities can be recycled at least three times. The degradation experiment showed thatthe micelles could degrade in different pH solutions with various degration rates(Vbasic>Vacidic>Vneutral).PLA was obtained by ROP of lactide in the presence of chain transfer agent TTC-OH.The triblock copolymers, poly (lactide)-block-poly (dimethylamino-2-ethylmethacrylate)-block-polyvinylbenzene acid (PLA-b-PDAMEMA-b-PVBA) was synthesizedby two-step RAFT based on DMAEMA and VBA monomers using PLA macromelecularmonomer as chain transfer agent. Structures of block copolymers were confirmed by FT-IR,1H-NMR and UV-Vis spectra. The self-assembly behavior was detected by Zeta potential andparticle sizer and Transmission Electron Microscopy (TEM). The results showed that thetriblock copolymers had glucose responsive property. The polyvinylbenzene acid segmentschanded from hydrophobic to hydrophilic after reacted with glucose. five g/L glucose solutionwas selected because high concentrated glucose could cause the micelles aggregation.