Synthesis of waterborne, branched, functional poly(urethane)s and their applications
Ongun, Nihan (2014) Synthesis of waterborne, branched, functional poly(urethane)s and their applications. [Thesis]
Polyurethanes are an important class of polymers that have wide application in a number of different industrial sectors. Their versatile chemistry enables researchers to design novel materials ranging from liquid, soft and rubbery solids to rigid thermoplastic and thermoset polymer for elastomeric materials, coating and adhesive. The present study focuses on synthesizing waterborne, branched and chemically functional polyurethanes with unique architectures via novel methodologies for coating and adhesive applications using the oligomeric A2 + Bn strategy where a multifunctional isocyanate Bn (n>2) was polymerized with an A2 oligomer or an A2 monomer. In order to prepare these novel polyurethanes in the form of waterborne dispersions, novel polyurethane ionomer architectures were designed with ionic groups either pendant along the polymer chain or placed at the chain end-groups. The effect of functionality, type and content of soft segment and type and location of emulsifying agent were critical parameters that were investigated in this study. The A2 + Bn strategy used in this study also permitted the control of the molar mass between branch points which led to interesting macromolecular properties, such as tunable mechanical properties, improved processibility, and a multitude of functional blocked isocyanate end-groups. Highly functional polyurethanes were formulated with hydroxyl functional components and model self-standing thermoset films were obtained, which showed interesting thermomechanical properties. Dynamic mechanical analyses demostrated that higher functionality increased the storage modulus by increasing crosslink density at equivalent soft segment molar mass whereas higher soft segment content decreased the storage modulus yet increased the elastic nature ofthese films. These characterizations results clearly revealed that novel synthethic approaches developed in this study were useful to prepare highly functional waterborne polyurethanes that could be used as a new component to prepare one component formulations with shelf-life stability to obtain thermoset films and coatings with tunable mechanical properties.
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