Polyurethane (PU)/acrylic hybrid dispersions are an important class of polymeric dispersions that are produced on an industrial scale. In this review, we detail the design and synthesis of PU/acrylic dispersions, with a particular focus on how the structure of the hybrid can be tuned toward commercial applications. After a brief introduction, we describe the building blocks used in each polymer and their role in the synthesis/application of the final dispersion. Subsequently, we discuss the range of procedures that have been developed for the synthesis of such hybrids and how the structure of the hybrids influences the physical properties of films cast from the dispersion. Finally, we highlight commercial applications of PU/acrylic hybrids, with a focus on potential future developments.

Polyurethane (PU)/acrylic waterborne hybrids are an attractive class of materials with wide application possibilities, but their synthesis typically requires significant quantities of solvent which has negative economic and environmental consequences. In this work, solvent-free and surfactant-free polyurethane (PU)/acrylic waterborne hybrids were obtained by synthesizing the PU prepolymer containing carboxylic groups directly in (meth)acrylic monomers that act as solvent. Then, the mixture is dispersed in water; the PU is chain-extended with diamines, and the (meth)acrylic monomers are polymerized. It was found that, against expectations, colloidal stability did not improve with the concentration of carboxylic groups that acted as stabilizing moieties. A combination of MALDI-TOF MS analysis and Monte Carlo simulations revealed that the highly heterogeneous compositions of the short chains of the PU prepolymer and their reaction with the chain-extender in the aqueous phase were responsible for lack of control of the colloidal properties. This problem was overcome by using more hydrophobic chain-extenders that decrease the fraction of PU chains in the water phase. In this way high-solid-content stable dispersions with controlled particle size were obtained. Finally, the properties of the PU/(meth)acrylic films were studied in terms of mechanical properties and water resistance.

Hybrid waterborne dispersions of polyurethane (PU)/poly(meth)acrylic are widely applied in coating and adhesive products, as well as in many other applications. The synergetic performance of the two component polymers is highly dependent on the ability to control the PU and (meth)acrylic network structure. In this work, the effect of grafting and the impact of macromolecular architecture on the particle and film morphology as well as on the properties of PU/(meth)acrylic hybrid films is investigated. It is shown that with grafting, the absolute molar mass distribution (MMD) is shifted toward higher values as the low molar mass PU chains become incorporated in the (meth)acrylic polymer network. Furthermore, by using different types of functional monomers, the nature of the MMD can be altered. Using transmission electron microscopy (TEM) analysis, it is demonstrated that more homogeneous particle and film morphologies are obtained in the case of grafted hybrids. Finally, the impact of network structure on tensile strength is outlined highlighting that grafted polymer films have higher Young's modulus and strain hardening than the non‐grafted ones.

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