Controlled Preparation Of Polyvinyl Alcohol-based Functional Materials With Catalysis Or Liquid Crystal Property

In this article, polyvinyl alcohol (PVA)-based macromonomer (PVAM) wasfirstly synthesized. Then it was used to prepare microgel carrier via inverse emulsionpolymerization. The microgels were applied to entrap α-amylase, nano-TiO2, andFe3O4/TiO2nanoparticles respectively, which rendered PVA-based microgels catalyticfunction. The effects of the molecular weight of and the concentration of PVAM onthe catalytic properties of the microgels were investigated. On the other hand, twodifferent methods were used to prepare PVA-based side-chain liquid crystal polymers,and their performances were preliminarily studied. The results were summarized asfollowing:1.Firstly, reversible addition-fragmentation chain transfer (RAFT)polymerization was adopted to synthesis well-defined PVA. Then unsaturatedPVA-based macromonomer (PVAM) was prepared via the esterification of PVA withmaleic anhydride (MA). After that, PVAM which contained a lot of double bonds andcarboxyl groups was cross-linked with acrylic acid (AA) through inverse emulsionpolymerization in the presence of α-amylase, and the microgels encapsulatingα-amylase were obtained. The structure and morphology of the intermediate, themicrogels were analyzed with gel permeation chromatography (GPC), Fouriertransform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), andscanning electron microscope (SEM). In addition, the properties of the microgels suchas swelling in water, encapsulation of α-amylase as well as catalysis ability wereinvestigated. It was found that the properties of the mirogels were controllable withthe concentration and molecular weight of PVAM. The content of carbon-carbondouble bonds was increased with increasing the molecular weight of PVA. As a result,the microgels’ particle size was decreased, while the swelling ratio, theamylase-loading capacity and the catalytic ability of the microgels increased. On theother hand, both the particle size and the swelling ratio of the microgel were increased,while their amylase-loading capacity and the catalytic ability were decreased with theincrease of the concentration of PVAM.2. PVA-based microgels containing nano-TiO2was prepared by inverse emulsionpolymerization in the presence of nano-TiO2, which provided a function ofphotocatalytic degradation of organic pollutants. Through the photocatalytic degradation of methyl orange, it was found that the TiO2loading capacity wasincreased with increasing the molecular weight of PVA, and so did theirphotocatalytic degradation performance. For the miacgels obtained from thederivatives of PVAc with number average molecular weight (Mn) of85600g/mol,TiO2loading rate is29.79%, and the photocatalytic degradation rate of methyl orangewas80.5%after3h-irradiation with the30W UV light in the presence of themicrogels. Moreover, the microgels can be recycled. The degradation rate of methylorange of4th catalytic run only reduced7%compared to the initial one.3. PVA-based microgels containing TiO2and Fe3O4nanoparticles were preparedby inverse emulsion polymerization, which provided a kind of magneticphotocatalytic materials. Through photocatalytic degradation of methyl orange, it wasfound that the TiO2/Fe3O4loading capacity was increased with increasing themolecular weight of PVA, so did their photocatalytic degradation performance. Forthe miacgels obtained from the derivatives of PVAc with Mn of85600g/mol, theloading rate was34.47%, and the photocatalytic degradation rate of methyl orangewas84.4%after3.5h-irradiation with the30W UV light. Magnetic microgels wereeasier to be recycled comparing with those only containing nano-TiO2. Thedegradation rate of methyl orange of4th catalytic run only reduced8%compared tothe initial one.4. Azo mesogenic units (AHAB) were incorporated onto PVA chains through twodifferent routes including thiol-ene Click reaction and RAFT polymerization. ThePVA-based liquid crystal polymers (VLCP) were analyzed with polarized opticalmicroscope (POM). It was found that the thiol-ene Click prepared VLCP was smecticphases, while RAFT polymerization prepared one was nematic phase. In addition,VLCPs were controllable with varying the molecular weight of PVA. The crystallinityof the sample prepared in the presence of0.1g RAFT agent was higher than thoseobtained under the other conditions.In short, PVA-based functional materials with catalytic or liquid crystalcharacters were prepared successfully. Their structures and performances werecontrollable. These made PVA, an inexpensive and available polymer, to be excellentmaterials and valuable.