Synthesis and phase separation during film formation of novel methyl methacrylate/ n-butyl acrylate/methacrylic acid (MMA/BA/MAA) hybrid urethane/acrylate colloidal dispersions

• Published in: Polymer (Guilford) 2004-08, Vol.45 (18), p.6235-6243
• Main Authors: Otts, Daniel B., Dutta, Sandipan, Zhang, Ping, Smith, Oliver W., Thames, Shelby F., Urban, Marek W.
• Format: Article
• Language: English
• Subjects: Applied sciences; Copolymerization; Exact sciences and technology; Organic polymers; Phase separation; Physicochemistry of polymers; Polyurethane; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2004.07.018

Hybrid acrylic/urethane colloidal dispersions were prepared by incorporation of a novel multifunctional urethane castor vinyl ether (UCVE) macromonomer derived from castor oil in acrylic latexes. Single-stage and two-stage semi-continuous emulsion polymerization processes were utilized to control placement of UCVE in colloidal dispersions with core/shell and spherical particle morphologies. While the single-stage process resulted in optically clear and chemically homogeneous films, the two-stage process led to heterogeneous film formation. Internal reflection infrared imaging (IRIRI) spectroscopic analysis of the film-air (F-A) interfaces revealed phase-separated urethane- and urea-rich domains ranging in size from approximately 4–40 μm. Based on these measurements, a model of film formation is proposed which incorporates the effect of exceedingly high shear conditions to achieve fine dispersions of UCVE. These experiments indicate that features of the single-stage process facilitate uniform dispersion of UCVE and efficient grafting between UCVE and the acrylic polymer matrix resulting in intimately mixed networks and homogeneous films.