Photo-cross-linkable PNIPAAm copolymers. 5. Mechanical properties of hydrogel layers
Photo-cross-linkable PNIPAAm copolymers. 5. Mechanical properties of hydrogel layers
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DOI：
10.1021/la030232m
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发表时间：
2003-12-23
期刊：
影响因子：
3.9
通讯作者：
Frank, CW
中科院分区：
文献类型：
--
作者：
Harmon, ME;Kucking, D;Frank, CW
利用原子力显微镜(AFM)研究了水中光交联温敏水凝胶层的力学性能。以N-异丙基丙烯酰胺和2-(二甲基马来酰亚胺)-N-乙基丙烯酰胺为单体，采用旋涂法制备了均匀的交联响应性水凝胶薄膜。用原子力显微镜(AFM)对这些薄膜进行了成像，并用力-距离曲线测量了薄膜随温度变化的弹性模量。水凝胶层的体积相变受固定底物的存在的限制，并且这些影响的长度尺度与模数有关。用表面等离子体共振和光波导谱对这些材料进行了研究，以确定聚合物的体积分数随温度的变化。该模数随聚合物体积分数的变化而变化，并与先前在块状水凝胶上的测量结果一致。考察了交联度和电离度对水凝胶模数的影响，并将这些结果与膨胀网络的橡胶弹性理论相比较，研究了水凝胶的形态。弹性活性网链的浓度低于预期，但在高于体积相变温度时，随着网络的崩塌而增加。
Atomic force microscopy (AFM) was used to study the mechanical properties of photo-cross-linked, temperature-responsive hydrogel layers in water. Photo-cross-linkable linear polymers based on N-isopropylacrylamide and 2-(dimethylmaleimido)-N-ethyl-acrylamide were spin-coated to produce uniform thin films of cross-linked responsive hydrogels. These films were imaged using AFM, and force-distance curves were used to measure the temperature-dependent elastic modulus. The volume phase transition of the hydrogel layers is constrained by the presence of a fixed substrate, and the length scale of these effects is related to the modulus. These materials were also studied with surface plasmon resonance and optical waveguide spectroscopy to determine the polymer volume fraction as a function of the temperature. The modulus varies as a function of the polymer volume fraction and is in good agreement with previous measurements on bulk hydrogels. The effect of the cross-linking density and degree of ionization on the modulus was investigated, and a comparison of these results to rubber elasticity theory for a swollen network was used to study the hydrogel morphology. The concentration of elastically active network chains is lower than expected but increases as the network collapses at temperatures above the volume phase transition temperature.