Thermosensive Properties Of PEG/PDMAEMA Block Copolymers Prepared By ATRP

In this paper, the macroinitiator (mPEG-Cl) was first prepared from methoxy poly(ethylene glycol) (mPEG) and chloroacetyl chloride. Then, atom transfer radical polymerization (ATRP) of styrene (St) was carried out using mPEG-Cl as initiator, cuprous chloride (CuCl) as catalyst, 2,2'-bipyridine (bpy) as ligand. GPC, IR and 1H-NMR analyses show that the synthesized mPEG-Cl macroinitiator and block copolymers (mPEG-b-PSt) have the desired structure with low polydispersities. In this way, the technology of ATRP which suit for our laboratory was built. mPEG-b-PSt nanoparticles were prepared by the nanoprecipitation technology with spherical figure of diameter about 70 nm.The macroinitiators (mPEG-Br or Br-PEG-Br) were first prepared from mPEG or PEG and 2-bromoisobutyryl bromide.Double hydrophilic block copolymers of 2-(dimethylamino) ethyl methacrylate (DMAEMA) and PEG were synthesized by ATRP using mPEG-Br or Br-PEG-Br macroinitiators of different molecular weights. GPC, FTIR, 1H-NMR analyses indicate that the copolymerization is well controlled with low polydispersities.The thermosensive properties of the PEG/PDMAEMA double hydrophilic block copolymers significantly depend on the concentration, pH, ionic strength of aqueous solution and chain architecture of the copolymers. PEG/PDMAEMA block copolymers with LCSTs around body temperature (30-37°C) can be prepared by adjusting those factors, which could be good candidates for drug delivery systems. The block copolymers dissolved in aqueous solution, on addition of poly (acrylic acid) (PAA), micellization occurred to form nanoparticles comprising polyelectrolyte complex cores and PEG shells. The size and size distribution were measured by BI-90Plus particle size analyzer ranged from 100 to 300 nm depending on the molar ratio between the oppositely charged subunits (DMAEMA to AA) and concentration, polydispersities less than 0.20.