Study On The Preparation Of An Affinity Changeable Core-shell Micro-latex And Its Application As Thermal Imaging Material

In this research, a novel affinity changeable core-shell microcapsule (latexparticle) was prepared along with its matched water-soluble resin and infraredabsorbing dye. Films constructed by these materials could undergo affinitychange, from hydrophilic to hydrophobic, by the action of heat or exposure toIR laser beam. This process neither involved chemical reactions nor requiredany post-treatment (such as development), suggesting that they wereenvironment friendly materials. This study consists of the following parts:(1) Molecular design and synthesis of reactive surfactants: methacrylatedpolyethyleneglycol 400 and amphiphilic reversible addition-fragmentationtransfer (RAFT) agents. Stable latexes with high solid content could beobtained in the presence of the RAFT agents (especially those derived from1-dodecanethiol), which had even stronger emulsifying capacity and weremore effective than methacrylated polyethyleneglycol 400.(2) Preparation and properties of core-shell latex particles with hydrophilicouter surface and hydrophobic core: two kinds of latex particles were preparedthrough soap-free emulsion polymerization by using methacrylatedpolyethyleneglycol 400 and the RAFT agents as reactive surfactant,respectively. Emphases were focused on the conditions of soap-free emulsionpolymerization under the action of the RAFT agent. The properties of theobtained latex particles such as emulsion stability and solid content, particlesize and distribution as well as thermo-induced affinity change were fullyinvestigated.(3) Molecular design and synthesis of water-soluble binder polymers. Inthis study, two water-soluble binder polymers were prepared, namely modifiedpoly(vinyl glycol) and modified epoxy phenolic resin. Results showed that themodified poly(vinyl glycol) was lack of enough aqueous solubility, whereas themodified phenolic resin was superior in all aspects and a promisingwater-soluble resin.(4) The choice and modification of infrared laser sensitive dye. Infraredsensitive dye employed in this study was an oil-based, aqueous insoluble typedye and could not be used directly in aqueous coating based imaginingmaterial system. So, one of the important works in this study was to convertthe oil-soluble dye into a water-soluble one. It was found that the dye turned tobe water soluble after treated with a poly(acrylic acid) oligomer (i.e. RAFTagent (â…£)).(5) Preliminary studies on the latex films for thermal imaging application.Experimental results indicated that the latex yielded uniform and fine filmswhen a small amount of binder resin was added, though it alone was of acertain film forming capacity. Before baked, the contact angle of the films withwater was around 600, after baked it increased to 1000. This result showed thatthe film affinity undergone great changes upon being heated and a thermalimaging media based on affinity change would be constructed.