Fabrication Of Functional Microgel Films And Materials

This thesis is focusing on the fabrication of functional microgel films and materials.In the first part,polyelectrolyte multilayer films composed of branched polyetyleneimine(bPEI)and poly(acrylic acid)(PAA)have been fabricated by layer-by-layer assembly(LbL)technique.Variations of pH value and ionic strength during film fabrication process have been proven to influence the film structure in previous studies.However,the research concerning the influence of temperature on film buildup has not been reported.Therefore,the structural and self-healing properties of the bPEI/PAA films fabricated under a range of different temperatures have been investigated in the current work.In the second part,although water-based adhesives have attracted much attention in recent years because of theirindustrial and importance,it is still lack of economic method with easily available raw materials to the fabrication of water-based adhesives.In this part,a kind of nontoxic and noncombustible water-based adhesive hydrogels has been fabricated successfully by using polyvinyl alcohol(PVA)and PAA as raw materials.Detailedstudies aiming at enhancing the adhesion by changing various influential factors have also been conducted.In chapter 1,we schematically introduced the traditional-LbL assembly and exponential LbL assembly,which is a rapid LbL assembly method.We described the process of exponential LbL assembly and applications of exponentially grown LbL-assembled films.We also introduced the methods for rapid preparation of polyelectrolyte hydrogels and their properties.In chapter 2,we systematically investigated influencesof temperature on the build-up of PAA/PEI films.At higher temperature,polyelectrolytes usually adopt a stretched coil structure with larger size in aqueous solution,and vice versa.Therefore,high temperature of the dipping solution tends to produce PAA/PEI films with larger thickness and rougher surface.We find the self-healing ability of the PAA/PEI films is also dependent on the temperature of the dipping solutions with higher ability to heal damage for films built at high temperature.When the PAA/PEI films were treated with aqueous solution of pH2.8,larger pores were found in the films prepared at higher temperature.In chapter 3,we prepared a kind of highly adhesive hydrogels by mixing aqueous solutions of PVA and PAA.The hydrogen-bonded hydrogels can adhesive for a variety of materials including glass,metals,plastics and woods.The hydrogels have several unique advantages as adhesives:First,the preparation method is simple which involves simply mixing aqueous PAA and PVA solutions and then collected by centrifugation.The fabrication process is environment friendly and the raw materials are commercially available.Secondly,the adhesives are applicable on a large variety of surfaces.Thirdly,the adhesion of the adhesive hydrogels is stable for a long time and water/heat-endurable.We believe that this kind of hydrogel can have potemtial industrial applications in the near future.