Dual Stimuli-Responsive Poly(2-hydroxyethyl methacrylate-co-methacrylic acid) Microgels Based on Photo-Cleavable Cross-Linkers: pH-Dependent Swelling and Light-Induced Degradation
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- 作者：Daniel Klinger ; Katharina Landfester
- 刊名：Macromolecules
- 出版年：2011
- 出版时间：December 27, 2011
- 年：2011
- 卷：44
- 期：24
- 页码：9758-9772
- 全文大小：1459K
- 年卷期：v.44,no.24(December 27, 2011)
- ISSN：1520-5835
文摘
Dual stimuli-responsive p(HEMA-co-MAA) microgels were prepared in a facile way by inverse miniemulsion copolymerization of 2-hydroxyethyl methacrylate (HEMA) with methacrylic acid (MAA) and two kinds of newly synthesized photodegradable cross-linkers. The pH-dependent swelling behavior induced by the protonation/deprotonation of the methacrylic acid groups in the network-forming polymer was investigated by means of the particle volume change as determined by DLS measurements. Photolytic degradation experiments were conducted by irradiation with UV light which led to particle disintegration caused by cleavage of the photolabile cross-linking points. The degradation behavior of the microgels was investigated with respect to degradation rates and changes in the degree of swelling. Those parameters were found to depend on the pH value of the solvent, the light intensities, and the irradiation wavelengths applied. For similar conditions, the degradation profile was demonstrated to strongly depend not only on the molecular structure of the cross-linking molecule but also on the molecular weight of the network-forming copolymers. The particular combination of the stimuli described is designed as a new strategy to two different swelling/degradation profiles. This dual stimuli-responsiveness was shown to enable the efficient loading and subsequent release of myoglobin as a model protein. Here a slow diffusion controlled release (induced by changes of the pH) was combined with a fast degradation controlled (induced by irradiation) on-demand release. This novel two-step release profile is proposed to bear great potential for delivery applications.