Synthesis and thermally responsive characteristics of dendritic poly(ether-amide) grafting with PNIPAAm and PEG

• Published in: Polymer (Guilford) 2007-02, Vol.48 (4), p.931-938
• Main Authors: Yang, Zhu, Zhang, Wenquan, Zou, Jianhua, Shi, Wenfang
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemical modifications; Chemical reactions and properties; Dendritic poly(ether-amide); Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Poly( N-isopropylacrylamide); Temperature-sensitive
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2006.12.052

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.