A novel hyperbranched multiarm copolymer of HBPO-star-PDEAEMA with a hydrophobic poly(3-ethyl-3-(hydroxymethyl) oxetane)(HBPO) core and many cationic poly(2-(N,N-diethylamino) ethyl methacrylate)(PDEAEMA) arms has been synthesized through an atom transfer radical polymerization(ATRP) method,and been applied to spontaneously reduce and stabilize gold nanoparticles(AuNPs) in water without other additional agents.The size of the nanoparticles could be effectively controlled at about 4 nm,and the nanoparticles are extremely stable in solution without aggregation even for one year.It was found that solution pH and the molar ratio of N/Au have certain effects on the size and stability of AuNPs.This work provides a simple method for the synthesis of uniform and highly stable AuNPs.
A novel temperature-responsive hyperbranched multiarm copolymer with a hydrophobic hyperbranched poly(3-ethyl-3-(hydroxymethyl)oxetane)(HBPO) core and thermosensitive poly(N-isopropylacrylamide)(PNIPAM) arms was synthesized via the atom transfer radical polymerization(ATRP) of NIPAM monomers from a hyperbranched HBPO macroinitiator.It was found that HBPO-star-PNIPAM self-assembled into multimolecular micelles(around 60 nm) in water at room temperature according to pyrene probe fluorescence spectrometry,1H NMR,TEM,and DLS measurements.The micelle solution showed a reversible thermosensitive phase transition at a lower critical solution temperature(LCST)(around 32°C) observed by variable temperature optical absorbance measurements.Variable temperature NMR and DLS analyses demonstrated that the LCST transition originated from the secondary aggregation of the micelles driven by increasing hydrophobic interaction due to the dehydration of PNIPAM shells upon heating.The drug loading and release properties of HBPO-star-PNIPAM micelles were also investigated using prednisone acetate as a model drug.The micelles showed a much improved drug encapsulation efficiency and temperature-dependent sustainable release behavior due to the special micellar structure.The micelles exhibited no apparent cytotoxicity against human HeLa cells.
GUO Bo,SUN XiaoYi,ZHOU YongFeng & YAN DeYue College of Chemistry and Chemical Engineering,Shanghai Jiao Tong University,Shanghai 200240,China
