Viscoelastic behaviour of self‐assembling polyurethane and poly(vinyl alcohol)

Abstract

The rheological behaviour of polyurethane (PU) and poly(vinyl alcohol) (PVA) was investigated in aqueous solution and the hydrogel state. The dependence of viscosity on polymer concentration is discussed. The formation of supramolecular structures induced by temperature increase or shear conditions was evidenced. In PU solutions, as temperature increases, a self‐assembling process occurs due to hydrogen bonding and hydrophobic interactions determining a thermoreversible hydrogel formation. In creep and recovery tests, the weak PU network presents high elasticity only at low shear stress (below 10 Pa); it recovers only 15%–20% of strain above 40 Pa and the hydrogel structure fails at high shear stress (above 150 Pa). Also, PU hydrogel is not able to recover its structure after being submitted to successive low and high deformations. In PVA solutions, a shear induced aggregation was observed at 37 °C. PVA hydrogels obtained by the freezing–thawing method present high elasticity and stability due to the strong polymer–polymer interactions established between the polymer chains. Physical networks based on PU/PVA mixtures synergistically combine the characteristics of the two polymers, showing high elasticity when a shear stress up to 3000 Pa is applied during the creep test followed by a fast recovery of the hydrogel structure after exhibiting successive levels of deformation (self‐healing ability). Therefore, these hydrogels are suitable materials for tissue engineering applications. © 2019 Society of Chemical Industry

Thermal, Mechanical and Chemical Analysis of Poly(vinyl alcohol) Multifilament and Braided Yarns

“…The rheological behaviour of PVA was investigated in an aqueous solution and in the hydrogel state. Bercea et al [27] found that in PVA solutions, shear-induced aggregation at 37 • C and PVA hydrogels present a high elasticity and stability due to the strong polymer-polymer interactions established between the polymer chains. According to those authors, PVA/polyurethane composite hydrogel presents high elasticity up to shear stress of 3 MPa, being followed by a rapid recovery of the hydrogel structure after showing successive levels of deformation.…”

Study on electroactive shape memory behaviors of polyvinyl alcohol/waterborne polyurethane/short carbon fiber composites

“…WPU solution and PVA were used as a cross‐linking agent in the progress of synthesizing waterborne polyurethane hydrogels, which confirmed that WPU and PVA formed a homogeneous miscible system through hydrogen bonds 14 . The viscosity behavior of PU and PVA aqueous solutions and the mixture of different compositions at 37°C were discussed 15 . The preparation of WPU/PVA composites could be divided into two methods: electrospinning and solution blending.…”

Supramolecular polymers with reversed viscosity/temperature profile for application in motor oils

“…The direct comparison of the linkers in A and B strongly suggests that the Thorpe-Ingold effect induced by the gemdimethyl unit is crucial for the supramolecular polymerization, thus indicating that indeed a ring-chain transformation is occurring. Next to the system described by Sijbesma and Meijer, other compounds have been described that influence the viscosity by dynamic supramolecular interactions, also leading to a viscosity increase at elevated temperatures [16][17][18].…”