Abstract
A series of thermally responsive dendritic core–shell polymers were prepared based upon dendritic poly(ether-amide) (DPEA), modified with carboxyl end-capped linear poly( N-isopropylacrylamide) (PNIPAAm-COOH) or both PNIPAAm-COOH and carboxyl end-capped methoxy polyethylene glycol (PEG-COOH) in different ratios via an esterification process to obtain DPEA–PNIPAAm or DPEA–PNIPAAm–PEG. Their molecular structures were verified by gel permeation chromatography, and 1H NMR and FTIR spectroscopy. The temperature-dependent characteristics study has revealed that DPEA–PNIPAAm exhibits a lower critical solution temperature (LCST) of about 34 °C, whereas DPEA–PNIPAAm–PEG polymers with the PNIPAAm/PEG ratio of about 1.0 and 0.4 possess about 36 °C and 39 °C, respectively, compared with 32 °C for homopolymer PNIPAAm. The critical aggregation temperature was investigated using fluorescence excitation spectrum of pyrene as a sequestered guest molecule based upon the sharp increase of the I 338/ I 333 value.
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