Facile hydrophobic modification of hybrid poly(urethane-urea)methacrylate aqueous dispersions and films through blending with novel waterborne fluorinated acrylic copolymers

Aqueous dispersions of fluorinated particles (PBF) based on copolymers of butyl acrylate (BA) with 2-(perfluorononenyloxyl)ethyl methacrylate (FNEMA), 2,2,3,3-tetrafluoropropyl acrylate (TFPA), and 2,2,3,3,4,4,5,5-octafluoropentyl acrylate (OFPA), respectively, were synthesized by emulsion polymerization in the presence of unfluorinated and fluorinated anionic surfactant binary mixtures. These fluorinated dispersions showed good to excellent colloidal stability, as determined by freeze-thaw, centrifugation, and critical coagulation concentration measurements. Blending of small amounts (1-10 wt%) of PBF latex particles with a waterborne hybrid poly(urethane-urea)-methacrylate (PUUA) resulted in a series of slightly fluorinated modified PUUA (MPUUA) with good film forming properties and low surface energy. The precursor PUUA had been synthesized separately by simultaneous chain extension of a poly(ester-urethane)-diisocyanate with ethylenediamine and soapless free radical polymerization of methyl methacrylate (MMA) swelling the resulting branched or slightly crosslinked poly(urethane-urea) (PUU) self-dispersible ionomer particles. The results of dynamic light scattering and Zeta potential measurements suggest that merging of PUUA and PBF particles and either engulfing or interdiffusion of the incompatible macromolecular phases occurred to some extent already in the colloidal state. Highly hydrophobic films with surface energy as low as 17 mJ/m2 were obtained upon hybridization of PUUA with the FNEMA copolymer. Thermal annealing allowed to minimize the effects of fast surface dynamics leading ultimately to water absorption, and to promote synergistic enhancement of the resulting hybrid film hardness, as required for coating applications

Strong Bioinspired Polymer Hydrogel with Tunable Stiffness and Toughness for Mimicking the Extracellular Matrix

Inspired by the delicate architecture of hyaline articular cartilage, we report on a biomimetic polymer hydrogel that incorporates strong intermolecular hydrogen bonding between urethane–urethane linkages as well as urethane–ester linkages. The resultant hydrogel, containing ≈75% water, can endure a compressive stress up to 56 MPa with a strain of 98%, and exhibit tunable compressive modulus (0.19–1.38 MPa), as well as toughness (3629–28290 J m^–2) within a wide range. The tensile strength and elastic modulus reach as high as 0.56 and 5.5 MPa, respectively. The high stiffness and toughness enable the gel to withstand cyclic compressive loadings without fracturing. Moreover, our hydrogel mimics the extracellular matrices of cartilage and bone tissues and provides biochemical and physical cues that support the three-dimensional proliferation of chondrocytes and osteogenic differentiation of preosteoblasts