Burcin Gacal

Sorption and Desorption of PVA-Pyrene Chains in and out of Agarose Gel

In situ steady-state fluorescence (SSF) measurement technique was applied to investigation of pyrene labeled Poly(vinyl alcohol) (PVA-Py) molecules diffusion in and out of agarose gels. Gel samples with four different concentration of agarose were prepared. PVA-Py was synthesized by “click” chemistry method and dissolved in water to use in diffusion experiments. The results were analyzed by using Fickian type diffusion model, and it was found that sorption and desorption processes of PVA-Py molecules in and out of agarose gel have two distinct regions for short and long diffusion times. Sorption and desorption coefficients were measured and it was seen that the diffusion rates were much larger at short times and at lower agarose concentrations.

Light-Induced Reactions of Benzoxazines and Derivatives

Publisher Summary This chapter describes photochemical routes for the incorporation of thermally polymerizable benzoxazine in linear and cross-linked polymeric structures. It focuses on the use of both the free radical and cationic photoinitiating systems for benzoxazine resins that provide some advantages or overcome existing problems and challenges in benzoxazine chemistry. The photochemical degradation and UV stability of benzoxazine resins are also discussed in this study. Benzoxazine resins are readily synthesized from benzoxazine monomers, either monofunctional or of higher functionality. It elaborates that photoinitiated polymerization is an important industrial process widely used in different applications. This process induces the polymer formation with a fast transformation of the liquid monomer into a solid film with tailored physical chemical and mechanical properties. This is a striking advantage for both the classical polymerization of monofunctional monomers and modern curing applications. Photopolymerizations are simply polymerization reactions initiated by light, typically in the ultraviolet or visible region of the light spectrum. Photoinitiated polymerization can be divided into two categories: free radical and cationic polymerizations. Deep curing using the described photoinitiating system followed by the thermal ring-opening of the incorporated benzoxazine groups provides highly dense cross-linked networks. The thermal cross-linking nature may be used to prepare high-performance thermoset polymers with diverse properties featuring self-supporting and flexible films. The hydrophilicity and wettability of benzoxazine films can also be changed by light. Such material is well-suited for applications such as coating and microelectronics where film formation is needed.