Next Article in Journal
Influence of a Crosslinker Containing an Azo Group on the Actuation Properties of a Photoactuating LCE System
Next Article in Special Issue
Flexible Transparent Electrode of Hybrid Ag-Nanowire/Reduced-Graphene-Oxide Thin Film on PET Substrate Prepared Using H2/Ar Low-Damage Plasma
Previous Article in Journal
Dynamic and Static Behavior of Hollow-Core FRP-Concrete-Steel and Reinforced Concrete Bridge Columns under Vehicle Collision
Previous Article in Special Issue
Enhanced Transdermal Permeability via Constructing the Porous Structure of Poloxamer-Based Hydrogel
Article Menu
Issue 12 (December) cover image

Export Article

Open AccessArticle
Polymers 2016, 8(12), 434;

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

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
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)
Full-Text   |   PDF [5073 KB, uploaded 14 December 2016]   |  


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 (Tg), 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 Tg 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 temperature-sensitive; pH-sensitive; CO2-sensitive; hydrogen bonding; copolymers

Graphical abstract

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Share & Cite This Article

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.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Polymers EISSN 2073-4360 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top