Asher Sanford A, Kimble Kyle W, Walker Jeremy P
Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania.
Chem Mater. 2008 Dec 2;20(24):7501-7509. doi: 10.1021/cm801519x.
We physically cross-linked a thermoreversible poly(vinyl alcohol) (PVA) hydrogel (TG) within a crystalline colloidal array (CCA) to form an enabling photonic crystal material. The TG consists of a physically cross-linked network formed in a process reminiscent of the well-known freeze-thaw physically cross-linking process, but which avoids solvent freezing which invariably disorders the CCA. These TGCCA can be inexpensively fabricated in any large volume and shape by avoiding the previous covalently polymerized CCA constraints that required thin sheet geometries to enable penetration of the UV light used to photopolymerize the system. This TG hydrogel enables rigidificaton of CCA crystals and subsequent chemical functionalization. In addition, an additional interpenetrating hydrogel can be polymerized within the TGPCCA. The TG can then be dissolved away by simply increasing the temperature. The TGCCA photonic crystal diffraction is highly efficient and similar to previously demonstrated PCCA with covalent cross-links. These TGCCA are stable for weeks or longer at room temperature and can be utilized as photonic crystal materials. They also can be irreversibly covalently cross-linked by using gluteraldehyde. These gluteraldehyde cross-linked TGCCA can be made into chemically responsive sensor photonic crystals by functionalizing the PVA hydroxyl groups with chemical recognition agents. We demonstrate low and high pH sensing by functionalizing with carboxylates and phenol derivatives, respectively.
我们在结晶胶体阵列（CCA）中对热可逆聚乙烯醇（PVA）水凝胶（TG）进行物理交联，以形成一种有实用价值的光子晶体材料。TG由一个物理交联网络组成，该网络的形成过程类似于众所周知的冻融物理交联过程，但避免了溶剂冻结，因为溶剂冻结总会扰乱CCA。通过避免先前共价聚合CCA的限制（即需要薄板几何形状才能使用于光聚合系统的紫外光穿透），这些TGCCA可以低成本地大量制造，且形状不限。这种TG水凝胶能够使CCA晶体固化并随后进行化学功能化。此外，可以在TGPCCA内聚合一种额外的互穿水凝胶。然后，只需提高温度就能溶解TG。TGCCA光子晶体衍射效率很高，与先前展示的具有共价交联的PCCA相似。这些TGCCA在室温下可稳定数周或更长时间，并可作为光子晶体材料使用。它们还可以通过使用戊二醛进行不可逆的共价交联。通过用化学识别剂对PVA羟基进行功能化，这些戊二醛交联的TGCCA可以制成对化学响应的传感器光子晶体。我们分别通过用羧酸盐和酚衍生物进行功能化，展示了对低pH和高pH的传感。
