Morphology control in surfactant free polyurethane/acrylic hybrid latices – The special role of hydrogen bonding

A series of surfactant free aliphatic PUD's, prepared with no organic solvent, were used as the first stage (seed) in the preparation of acrylic hybrid latices. The acrylic component consisted of various comonomers of methyl methacrylate, n-butyl acrylate and styrene. By using a combination of film formation, DSC, TEM, and SEM measurements, the composite latex morphologies were characterized for a wide variety of experimental conditions. Essentially all latex reactions resulted in non-equilibrium morphologies with a great deal of mixed polymers in the particles, but all reactions yielded colloidally stable latices at 20% total solids. Hydrogen bonding between the amine units in the PU and the carbonyl groups on the acrylic polymer chains was responsible for the lack of polymer phase separation in the particles. Removing the carbonyl groups in the second stage monomer and/or thermally annealing the finished latex or dried films above 130 °C, allowed nearly complete phase separation to occur. In addition it was found that all of the PU based latex particles contained surprisingly large amounts of water. [Display omitted] •A wide variety of segmented PUD/acrylic hybrid latices were synthesized.•DSC identified large amounts of phase mixing within all hybrid latex particles.•Hydrogen bonding between carbonyl and amine groups restricts phase separation.•Annealing >130 °C reduced H bonding and promoted phase separation (DSC and TEM).•Significant water content is present within PUD and PU/Ac hybrid latex particles.