Preparation of Hyperbranched Graft Copolymers

To study the solution property of novel amphiphilic hyperbranched graft copolymer chains, we further prepared amphiphilic hyperbranched poly(acrylic acid) grafted with short polystyrene copolymer (HB-PAA- -PS) with a large hydro-phihc hyperbranched PAA core and short hydrophobic PS grafted chains. The copolymer chains with different branching degrees of PAA core were carefully prepared and well confirmed by SEC, H NMR, and FT-IR. As well, the 

well-defined Seesaw-type macromonomer alkyne-(PtBA39-N3)2 was prepared via ATRP and azidation reaction. SEC curve (Fig. 4.16) demonstrates the prepared macromonomer aIkyne-(PtBA39-N3)2 is narrowly distributed with a poly-dispersity index of -1.09. The absolute DP value was calculated to be 

Then we directly carried out click reaction between 40-fold excess of alkyne-PS and alkyne-(PlBA-N3)2 to result in PS-PfBA-PS triblock while 5-fold excess is not enough to suppress the self-polycondensation of alkyne-(PiBA-N3)2 chains (Fig. 4.16a). However, one problem to deal with is how to remove the excess of alkyne-PS chains from the mixtures of reaction products. Further TFA de-protection of tertiary butyl group into carboxyl group leads to the corresponding HB-(PAA) -g-(PS)n+i and PS-PAA-PS, which would facilitate the removal of excess alkyne-PS chains. In the precipitation-purification step, we repeated dissolution-precipitation cycle three times to remove excess alkyne-PS, where cyclohexane was used as precipitant, which is a good solvent for short PS, but a very poor solvent for HB-(PAA) -g-(PS) +i and PS-PAA-PS copolymers. Finally, purified white-powder of amphiphilic copolymer HB-(PAA)io-g-(PS)n = 6.30 x 10 g/mol), HB-(PAA)47- -(PS)48 (Afw = 2.60 X 10 g/mol) and their linear triblock analogues PS-PAA-PS (Afw = 7.50 X 10 g/mol) were obtained. 

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Preparation of Hyperbranched Graft Copolymers Table 4.2 SEC characterization result of (co)polymer chains... 

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