Study On Synthesis And Properties Of Water-soluble Hyperbranched Photosensitive Polysiloxane Urethane Acrylate

Photosensitive polysiloxane has been paid much attention as a solderresist ink in electronic industries in recent years due to its uniqueproperties such as flexibility, heat resistance, good weatherability, benignenvironmental effect, energy savings, and improved workability, etc.Hyperbranched polymers, which are dendritic polymers, have beenstudied extensively because of their highly branched architecture, leadingto high solubility, low melting viscosity, large amount of terminalfunctional groups, and so forth. Introduction of hyperbranched structureinto UV-curable polysiloxane molecule could obtain oligomers with lowviscosity and high functionality. Meanwhile, introduction of water-solublestructure into UV-curable polysiloxane molecule could obtain oligomerswith water-soluble. Then water could replace organic solvent, reducingpollution, when the materials are used. The purpose of this paper is todesign and synthesize a novel water-soluble hyperbranchedphotosensitive polysiloxane (WPHBPSUA) with low viscosity, good water-solubility, and high functionality for the solder resist ink. Also, therelationship between structures and properties has been studied, and thatcan be theoretical and technical basis for expanding UV-curingpolysiloxanes application field. The specific work and study results are asfollows:1. WPHBPSUA was synthesized via a simple and convenient synthesismethod, namely the hydroxylic hyperbranched polyesters cores,polysiloxane arms, dimethylol propionic acid units and curable acrylicdouble bonds were linked together via the reaction of–NCO groups fromisophorone diisocyanate and–OH groups. The degree of branching ofWPHB6PSUA, WPHB12PSUA, and WPHB24PSUA is6,12, and24,respectively. The structures of WPHBPSUA were characterized byFourier transform infrared spectroscopy(FTIR), gel permeationchromatography(GPC), and1H nuclear magnetic resonancespectroscopy(1H NMR).2. The synthesized WPHBPSUA has a good compatibility with all kindsof monomers. The viscosity（350-550mPa s） of WPHBPSUA system isevidently lower than the viscosity （7400mPa s）of linear PSUA system.3. The effect of reactive monomers and structure of oligomers on thephotosensitive properties of water-soluble hyperbranched UV-curablepolysiloxane urethane acrylate oligomers was investigated by RT-IR.Photopolymerization kinetics of WPHB6PSUA, WPHB12PSUA, WPHB24PSUA and the commercial linear flexible resin OAK-27showedthat WPHBPSUA exhibited higher polymerization rate and double bondconversion than OAK-27.4. The microstructure and physical mechanical properties of UV-curedfilms were characterized, such as microstructure morphology, elementanalysis on the surface of the films, water resistance, volumetricshrinkage, chemical resistance，tensile strength，hardness, adhesion,thermal resistance, glass transition temperature and so on. It is provedthat the degree of cross-linking and Si content of the UV-curedWPHBPSUA films increased with the increase of the degree of branchingof WPHBPSUA oligomers, leading to excellent flexibility, adhesion,toughness and heat resistance of UV-cured WHBPSUA films. Thevolumetric shrinkage was about3.2-7.0%. Thermal property of the curedfilms was good and weight loss of the cured films at300℃was lowerthan7%(the weight loss of commercial linear flexible resin OAK-27at300℃was25.76%). In addition, all the synthesized oligomers werecapable of securing accuracy of pattern，and it has prospective applicationin solder mask field.