### SiO2-HA/PNIPAm核壳温敏微凝胶的合成及其溶胀性能

1. 华东理工大学结构可控先进功能材料及其制备教育部重点实验室和化学系 上海 200237
• 投稿日期:2014-04-13 发布日期:2014-05-22
• 通讯作者: 徐首红 E-mail:xushouhong@ecust.edu.cn
• 基金资助:
项目受国家自然科学基金（Nos.21276074，91334203）和中央高校基本科研业务费资助.

### Synthesis and Swelling Behavior of SiO2-HA/PNIPAm Core-shell Structured Thermoresponsive Microgels

Li Xiangye, Lian Cheng, Zhi Dongyan, Xu Shouhong, Liu Honglai

1. Key Laboratory for Advanced Materials and Department of Chemistry, East China University of Science and Technology, Shanghai 200237, China
• Received:2014-04-13 Published:2014-05-22
• Supported by:
Project supported by the National Natural Science Foundation of China (Nos.21276074, 91334203) and the Fundamental Research Funds for the Central Universities of China.

A series of thermoresponsive core-shell microgels were synthesized using SiO2 as core and hybrid gel (hyaluronate/poly(N-isopropylacrylamide) (HA/PNIPAm)) as shell.SiO2 particles were modified by KH550 to get -NH2 groups, which could be protonized in acid condition.So that they could be covered by HA chains through electrostatic force.Then, HA was grafted using glycidyl methacrylate (GMA) to obtain C=C groups for the next synthesis of HA/PNIPAm hybrid gel.The modification degree of C=C was determined through 1H nuclear magnetic resonance spectroscopy (1H NMR).Fourier-transform infrared spectra (FT-IR) were used to monitor each synthesis step.Transmission electron microscopy (TEM) images showed that SiO2-HA/PNIPAm microgels were almost monodispersed and possessed perfect core-shell structures.Thermoresponsive behaviors of microgels were investigated using micro-differential scanning calorimetry (Micro-DSC), which showed that the lower critical solution temperature (LCST) values were almost the same, around 34±0.1 ℃, regardless of the synthetic parameters.The thixotropy of SiO2-HA/PNIPAm microgels was studied using rheometer.It turned out that the microgels possessed negative thixotropy.Moreover, when the temperature was higher than LCST, the thixotropy was better than that of lower temperature.The swelling behaviors of SiO2-HA/PNIPAm microgels were evaluated by combining experiment methods and theoretical calculation.Dynamic light scattering (DLS) was used to analyze the swelling behavior of microgels with the increase of temperature.The DLS results showed that microgels possessed good thermoresponsive behavior with a LCST at about 34 ℃, which was in accordance with that determined by Micro-DSC.The hydrodynamic diameter (d) was found to be dependent on the size of core, the Mw of HA and the amount of PNIPAm.Theoretical calculation was carried out using a lattice molecular thermodynamic model based on our previous works, it showed that the calculated results were in good agreement with the experimental data.The results indicated that the model could predict the swelling behavior of thermoresponsive core-shell structured microgel using fewer model parameters.This work will provide fundamental reference for further research.