Temperature-, pH- and CO2-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures

Shieh, Yeong-Tarng; Lin, Pei-Yi; Chen, Tao; Kuo, Shiao-Wei

doi:10.3390/polym8120434

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Temperature-, pH- and CO₂-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures

^1,*,

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and

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Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan

Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan

Ningbo Institute of Material Technology and Engineering, Key Laboratory of Graphene Technologies and Applications of Zhejiang Province, Chinese Academy of Science, Zhongguan West Road 1219, Ningbo 315201, China

Authors to whom correspondence should be addressed.

Academic Editor: Jinlian Hu

Polymers 2016, 8(12), 434; https://doi.org/10.3390/polym8120434

Received: 14 November 2016 / Revised: 6 December 2016 / Accepted: 7 December 2016 / Published: 14 December 2016

(This article belongs to the Special Issue Functionally Responsive Polymeric Materials)

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Abstract

A series of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAAm-co-PAA) random copolymers were synthesized through free radical copolymerization in MeOH. The incorporation of the acrylic acid units into PNIPAAm tended to enhance the glass transition temperature (T_g), due to strong intermolecular hydrogen bonding between the amide groups of PNIPAAm and the carboxyl groups of PAA, as observed using ¹H nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopic analyses. The lower critical solution temperature (LCST) increased upon increasing the pH of the aqueous solution containing PNIPAAm-co-PAA because the COOH groups of the PAA segment dissociated into COO⁻ groups, enhancing the solubility of the copolymer. In addition, high-pressure differential scanning calorimetry revealed that the LCSTs of all the aqueous solutions of the copolymers decreased upon increasing the pressure of CO₂, suggesting that CO₂ molecules had displaced H₂O molecules around the polar CONH and COOH groups in PNIPAAm-co-PAA, thereby promoting the hydrophobicity of the copolymers in the aqueous solution. In addition, the values of T_g of a film sample increased upon treatment with supercritical CO₂, implying that intermolecular interactions in the copolymer had been enhanced after such treatment. View Full-Text

Keywords: temperature-sensitive; pH-sensitive; CO₂-sensitive; hydrogen bonding; copolymers

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MDPI and ACS Style

Shieh, Y.-T.; Lin, P.-Y.; Chen, T.; Kuo, S.-W. Temperature-, pH- and CO₂-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures. Polymers 2016, 8, 434. https://doi.org/10.3390/polym8120434

AMA Style

Shieh Y-T, Lin P-Y, Chen T, Kuo S-W. Temperature-, pH- and CO₂-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures. Polymers. 2016; 8(12):434. https://doi.org/10.3390/polym8120434

Chicago/Turabian Style

Shieh, Yeong-Tarng, Pei-Yi Lin, Tao Chen, and Shiao-Wei Kuo. 2016. "Temperature-, pH- and CO₂-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures" Polymers 8, no. 12: 434. https://doi.org/10.3390/polym8120434

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Temperature-, pH- and CO₂-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures

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