光引发接枝聚合调控水凝胶表面疏水性能
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摘要
利用光引发表面聚合的方法在水凝胶表面接枝疏水基团,赋予水凝胶表面疏水性能,其原理是基于TypeⅡ型光引发剂的夺氢光引发机理,夺取水凝胶高分子链中叔胺邻位碳原子上的氢原子,使得该碳原子成为自由基,引发丙烯酸十八酯增长聚合,从而在水凝胶表面以化学键铆接上一层疏水的高分子层。通过红外(FT-IR)、接触角和水滴渗入时间测试,探讨了光引发接枝条件对水凝胶表面疏水性能的影响,结果表明:在水凝胶中加入含有叔胺基团的甲基丙烯酸二甲氨基乙酯作为TypeⅡ型光引发的助引发剂和接枝位点,与疏水单体丙烯酸十八酯发生聚合反应可以形成稳固的疏水层,有效增强水凝胶的疏水性;采用N,N′-亚甲基双丙烯酰胺(BIS)交联剂能使疏水层形成交联网络结构,提高接枝层的致密性和疏水性,对水滴的渗入起到更好的阻碍作用。
Hydrogels, which usually comprise hydrophilic polymers and water, are generally able to act as biomaterials, due to their high water content, soft nature, and 3 D porous structure. However, the surface of many biological tissues is hydrophobic. In this work, a hydrophobic polymer layer was grafted on the surface of a hydrogel through Type Ⅱ photopolymerization in an attempt to increase the hydrophobic properties of the hydrogel surface. Isopropyl thioxanthone(ITX) is a Type Ⅱ photoinitiator, with an excitation wavelength of 405 nm. ITX exhibits no triggering activity but abstracts H atoms from amines and the amines are the final radicals initiating photopolymerization. Through this photo-grafting method, a hydrophobic polymer, poly(octadecyl acrylate) was grafted on the surface of a hydrogel. A cross-linking polymer layer can be formed by using BIS cross-linking agent, which increases compactness and the hydrophobic properties of the polymerized surface, thus effectively blocking infiltration of water drops. The conversion of the photopolymerization was monitored by FT-IR and the effect of varying the photo-grafting conditions on the surface hydrophobic properties of the hydrogel was studied by the measuring the contact angle and infiltration time of water drops. The results show that the layer of poly(octadecyl acrylate) effectively improves the hydrophobic properties of the hydrogel.
Hydrogels, which usually comprise hydrophilic polymers and water, are generally able to act as biomaterials, due to their high water content, soft nature, and 3 D porous structure. However, the surface of many biological tissues is hydrophobic. In this work, a hydrophobic polymer layer was grafted on the surface of a hydrogel through Type Ⅱ photopolymerization in an attempt to increase the hydrophobic properties of the hydrogel surface. Isopropyl thioxanthone(ITX) is a Type Ⅱ photoinitiator, with an excitation wavelength of 405 nm. ITX exhibits no triggering activity but abstracts H atoms from amines and the amines are the final radicals initiating photopolymerization. Through this photo-grafting method, a hydrophobic polymer, poly(octadecyl acrylate) was grafted on the surface of a hydrogel. A cross-linking polymer layer can be formed by using BIS cross-linking agent, which increases compactness and the hydrophobic properties of the polymerized surface, thus effectively blocking infiltration of water drops. The conversion of the photopolymerization was monitored by FT-IR and the effect of varying the photo-grafting conditions on the surface hydrophobic properties of the hydrogel was studied by the measuring the contact angle and infiltration time of water drops. The results show that the layer of poly(octadecyl acrylate) effectively improves the hydrophobic properties of the hydrogel.
引文
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[2] 饶志高, 周明元, 张建清, 等. 水凝胶的制备及其在医学上的运用[J]. 中国医疗器械信息, 2007, 13(11): 17- 20. RAO Z G, ZHOU M Y, ZHANG J Q, et al. The preparation of hydrogels and its application in medical science[J]. China Medical Device Information, 2007, 13(11): 17- 20. (in Chinese)
[3] LAI S K, WANG Y Y, HIDA K, et al. Nanoparticles reveal that human cervicovaginal mucus is riddled with pores larger than viruses[J]. Proceedings of the National Academy of Sciences of the United States of America, 2010, 107(2): 598- 603.
[4] 潘婷婷. 温度和pH双重响应性水凝胶的制备及其药物控制释放研究[D]. 合肥: 中国科学技术大学, 2011. PAN T T. Synthesis of dual thermo- and pH-sensitive network-grafted hydrogels as drug delivery system[D]. Hefei: University of Science and Technology of China, 2011. (in Chinese)
[5] 张敏, 李碧婵, 陈良壁. 互穿网络聚合物水凝胶的制备及其吸附研究进展[J]. 化工进展, 2015, 34(4): 1043- 1049. ZHANG M, LI B C, CHEN L B. Progress in preparation of interpenetrating polymer network hydrogels and their application in adsorption[J]. Chemical Industry and Engineering Progress, 2015, 34(4): 1043- 1049. (in Chinese)
[6] 王南平, 余晓冬, 陈洪渊. 环糊精超分子化学研究的新进展[J]. 化学研究与应用, 2001, 13(1): 27- 32. WANG N P, YU X D, CHEN H Y. Progress in the supramolecular chemistry of cyclodextrin[J]. Chemical Research and Application, 2001, 13(1): 27- 32. (in Chinese)
[7] 王敏. 攻克塑料薄膜表面处理难题[J]. 包装世界, 2004, 4: 56. WANG M. Overcoming the difficulties of plastic film surface treatment[J]. Packaging World, 2004, 4: 56. (in Chinese)
[8] 孙扶. 协同ATRP、点击化学及超临界二氧化碳技术制备基于水凝胶和聚苯胺的复合材料[D]. 上海: 华东理工大学, 2010. SUN F. Preparation of composites based on hydrogels and polyaniline by combining ATRP, click chemistry and supercritical carbon dioxide techniques[D]. Shanghai: East China University of Science and Technology, 2010. (in Chinese)
[9] YANG P, XIE J Y, YANG W T. A simple method to fabricate a conductive polymer micropattern on an organic polymer substrate[J]. Macromolecular Rapid Communications, 2006, 27: 418- 423.
[10] ZHAO H C, YANG P, DENG J P, et al. Fabrication of a molecular-level multilayer film on organic polymer surfaces via chemical bonding assembly[J]. Langmuir, 2007, 23(4): 1810- 1814.
[11] YANG P, DENG J Y, YANG W T. Confined photo-catalytic oxidation: a fast surface hydrophilic modification method for polymeric materials[J]. Polymer, 2003, 44: 7157- 7164.
[12] WU S P, ZHU X Q, YANG J L, et al. A facile photopolymerization method for fabrication of pH and light dual reversible stimuli-responsive surfaces[J]. Chem Comm, 2015, 51(26): 5649- 5651.
[13] DONG Y G, ZHU X Q, SHI F, et al. Surface photo-anchored PNIPAM crosslinked membrane on glass substrate by covalent bonds[J]. Applied Surface Science, 2014, 307: 7- 12.
[14] ZHANG J J, NIE J, ZHU X Q. Surface-selective grafting of crosslinking layers on hydrogel surfaces via two different mechanisms of photopolymerization for site-controllable release[J]. Macromolecular Rapid Communications, 2018, 39(20): 1800144.