Thermally crosslinkable poly(N-isopropylacrylamide) copolymers: Synthesis and characterization of temperature-responsive hydrogel

• Published in: Materials chemistry and physics Vol. 134; no. 2-3; pp. 1208 - 1213
• Main Authors: Chuang, Wen-Ju, Chiu, Wen-Yen, Tai, Horng-Jer
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2012
• Subjects: Clouds; Copolymers; Crosslinking; Differential scanning calorimetry; Heat treatment; Hydrogels; Monitoring; Polymer; Swelling; Swelling ratio; Thermal properties; Thermal properties; Differential scanning calorimetry; Polymer; Heat treatment
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2012.04.030

Thermally crosslinkable copolymers of N-isopropylacrylamide (NIPAAm) and N-Methylol acrylamide (NMA), a thermal crosslinker, were prepared by redox polymerization. The aqueous solutions of the copolymer were temperature responsive, and they showed phase separation behavior. The corresponding phase transition temperatures were detected by UV–visible spectroscopy and differential scanning calorimetry (DSC). The cloud points increased with increasing content of NMA from 32°C of pure polyNIPAAm to 48°C for poly(NIPAAm-co-NMA) with 30mol% NMA. The crosslinking capability of the resulting polymers with different NMA contents was evaluated by monitoring their gel fractions and swelling ratios after crosslinking. The equilibrium swelling behaviors of the poly(NIPAAm-co-NMA) hydrogels were also investigated as a function of curing time. The results showed the hydrogels cured at shorter times or lower temperatures had lower gel fractions and higher swelling ratios. The introduction of a crosslinking structure into the temperature-responsive polyNIPAAm controlled the swelling capability and the cloud point of the crosslinked hydrogels. ► N-(Methylol acrylamide) performs the crosslinking function at high temperature. ► The swelling ratio of the copolymer hydrogels is strongly dependent on NMA molar content, curing time and curing temperature. ► The cloud points of crosslinked copolymers shifted to lower temperatures due to the increasing crosslinking density.