Synthesis Of Amphiphilic Block Copolymer And Its In Situ Self-assembly

Polymeric nanomaterials contain a variety of advantages of polymer and nanomaterials, such as a wide range of source materials, versatile constructions and the effect of small size. They have attracted continuing interests due to their potential application in delivery and release of drugs, smart surface coatings, catalytic agents and so on. Self-assembly of block copolymers in solution, which was complained with the complex steps, time-comsuming and low concentration of nanoparticles has been a traditional method for the construction of polymeric nanomaterials. In situ self-assembly of block copolymer induced by reversible addition-fragmentation chain transfer(RAFT) polymerization has overcome the defects of traditional self-assembly method and becomes an effective method to synthesize polymeric nanomaterials. In this paper, we synthesize different amphiphilic block copolymers by RAFT polymerization. In situ self-assembly induced by a mixture of two macromolecular chain transfer agents co-mediated RAFT polymerizations were conducted at different conditions for obtaining the functional nanoparticles of different morphologies. The main contents and results of this paper are listed as follows:1. Water dispersible latex particles with randomly mixed shells or chain segregated surface were synthesized from one-pot reversible addition–fragmentation chain transfer heterogeneous polymerization of benzyl methacrylate(Bz MA) using a mixture of poly(glycerol monomethacrylate)(PGMA) and poly(2,3-bis(succinyloxy)propyl methacrylate)(PBSPMA) macromolecular chain transfer agents. In methanol, the two in situ synthesized PGMA-b-PBz MA and PBSPMA-b-PBz MA diblock copolymers coaggregated into spherical micelles, which contained PBz MA core and discrete PGMA and PBSPMA nanodomains on the shell. In contrast, in water–methanol mixture(V/V =9/1), latex particles with homogeneous distribution of PGMA and PBSPMA polymer chains on the shell were obtained. The reasons leading to formation of latex particles with homogenous or chain-segregated surface were discussed, and polymerization kinetics and physical state of PBSPMA in methanol and water-methanol mixtures were ascribed. These polymeric micelles with patterned functional group on the surface are potentially important for application in supracolloidal hierarchical assemblies and catalysis.2. For the first time, diblock copolymer nanoparticles of various morphologies, including sphere, worm and vesicle with randomly mixed shells were synthesized from one-pot RAFT heterogeneous polymerization of benzyl methacrylate(Bz MA) using a mixture of poly(2-hydroxypropyl methacrylate)(PHPMA) and poly(2-(succinyloxy)propyl methacrylate)(PSPMA) macromolecular chain transfer agents. Two effects, degree of polymerization(DP) of the PBz MA block and total concentration, on the morphology of nanoparticles were discussed. Like the approaches using one maromolecular chain transfer agent had described in the literature, the self-assembly copolymer(PHPMA37/PSPMA37-b-PBz MA) spheres, worms or vesicles were obtained with the systematic increase in the DP of the PBz MA block. Also, the worm nanoparticles and vesicles were obtained with the increase in total concentration from 15% to 20%. Interesting, the free standing physical hydrogel of the worm nanoparticles latex was formed, probably due to the interworm entanglements.3. PGMA and PBSPMA macromolecular chain transfer agents co-mediated RAFT polymerizations of HPMA were conducted in aqueous, which is an economic and environmental solvent. The effects of DP of PHMA on the copolymer nanoparticles were discussed. Copolymer spheres of different characteristics of shells were obtained with different DP of the PHPMA bock from 99 to 346.