Dual‐Crosslink Physical Hydrogels with High Toughness Based on Synergistic Hydrogen Bonding and Hydrophobic Interactions

• Published in: Macromolecular rapid communications. Vol. 39; no. 14; pp. e1700806 - n/a
• Main Authors: Chang, Xiaohua, Geng, Yuhui, Cao, Heqing, Zhou, Jian, Tian, Ye, Shan, Guorong, Bao, Yongzhong, Wu, Zi Liang, Pan, Pengju
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.07.2018
• Subjects: Acrylates - chemistry; Acrylic acid; Chains; Chemical bonds; Cross-Linking Reagents - chemistry; Crosslinking; Crystallization; dual crosslinks; External stimuli; Hydrogels; Hydrogels - chemistry; Hydrogen; Hydrogen Bonding; Hydrogen bonds; Hydrophobic and Hydrophilic Interactions; Hydrophobicity; Mechanical properties; Metal ions; physical hydrogels; Polymers - chemistry; Pyrimidinones - chemistry; Shape memory; Stimuli; Synergistic effect; shape memory; dual crosslinks; mechanical properties; physical hydrogels
• ISSN: 1022-1336; 1521-3927; 1521-3927
• DOI: 10.1002/marc.201700806

Constructing dual or multiple noncovalent crosslinks is highly effective to improve the mechanical and stimuli‐responsive properties of supramolecular physical hydrogels, due to the synergistic effects of different noncovalent bonds. Herein, a series of tough physical hydrogels are prepared by solution casting and subsequently swelling the films of poly(ureidopyrimidone methacrylate‐co‐stearyl acrylate‐co‐acrylic acid). The hydrophobic interactions between crystallizable alkyl chains and the quadruple hydrogen bonds between ureidopyrimidone (UPy) motifs serve as the dual crosslinks of hydrogels. Synergistic effects between the hydrophobic interactions and hydrogen bonds render the hydrogels excellent mechanical properties, with tensile breaking stress up to 4.6 MPa and breaking strain up to 680%. The UPy motifs promote the crystallization of alkyl chains and the hydrophobic alkyl chains also stabilize UPy–UPy hydrogen bonding. The resultant hydrogels are responsive to multiple external stimuli, such as temperature, pH, and ion; therefore, they show the thermal‐induced dual and metal ion‐induced triple shape memory behaviors. A novel and simple approach is reported to prepare tough physical hydrogels by solution casting and subsequently swelling the films of poly(ureidopyrimidone methacrylate‐co‐stearyl acrylate‐co‐acrylic acid). Synergistic effects between the hydrophobic interactions of crystallizable alkyl chains and hydrogen bonding interactions between the ureidopyrimidone motifs endow the hydrogels with excellent mechanical properties.