Small-Angle Neutron Scattering Study on Defect-Controlled Polymer Networks

Abstract

Tetra-PEG gels are classified to near-“ideal” networks with significantly low inhomogeneities, which were confirmed by small-angle neutron scattering (SANS). In this study, we systematically introduced two types of defects into Tetra-PEG gels and investigated effects of defects on structure. First, we prepared defect-rich networks by simply reducing prepolymer concentration, and observed the evolution of network structure by time-resolved SANS during gelation process. In this case, both the scattering intensity and the correlation length increased with reaction time in the ϕ < ϕ* region, while they scarcely changed in the ϕ > ϕ* region. Here, ϕ and ϕ* are the polymer volume fractions at observation and that at chain-overlap concentration, respectively. Second, we prepared “p-tuned” Tetra-PEG gels by tuning the reaction probability, p, and soaked them in water to expose the inhomogeneities. It was revealed that SANS profiles of as-prepared gels did not change noticeably, while those of swollen gels systematically changed with decreasing p. On the basis of these results, we discuss the relationship between the defects of polymer network and inhomogeneities by using simple schematic pictures of polymer network.

Heterogeneity and its Influence on the Properties of Difunctional Poly(ethylene glycol) Hydrogels: Structure and Mechanics

“…First, polymeric precursors below the overlap concentration form sparse networks when they react because they cannot fill the entire volume. 51 Specifically, de Gennes proposed that polymer chains forced to be nearby due to cross-linking have a concentration proportional to the overlap concentration. 33 This will necessarily create regions of depleted polymer elsewhere in the material.…”

Exploration of Ideal Polymer Networks

“…This is why a very uniform network is formed . A SANS study on defect‐controlled Tetra‐PEG gels also indicates such a reaction‐controlled kinetics and formation of inhomogeneity‐free networks …”

“…Tetra‐PEG ion gels are non‐volatile gels and they keep softness in the air. By playing with the degree of cross‐linking, p , controlled‐defect networks are prepared with which percolation problems can be revisited . Furthermore, by introducing hetero‐co‐prepolymers, various types of novel gels (networks) have been developed, such as non‐swellable implantable gels, very tough “fuse”‐link gels, and amphiphilic conetworks .…”

“…In order to answer this question, (1) we investigated the gelation kinetics and structure evolution of Tetra‐PEG gel . Furthermore, we carried out (2) the network structure of defect‐controlled polymer networks, and (3) experimental and theoretical aspects of the mechanical properties of tetra‐functional polymer networks . (4) Some practical applications of ideal networks including high‐performance uniform ion‐gels are also demonstrated.…”

Multiscale characterization of semicrystalline polymeric materials by synchrotron radiation X‐ray and neutron scattering

“…On the one hand, the advanced synchrotron radiation (SR) facilities provide good opportunities to investigate the dynamic structural evolutions under processing and service states of polymeric materials . Neutron scattering, on the other hand, is a powerful method to investigate chain conformation and nanostructures in multicomponent systems by means of labeling via hydrogen/deuterium exchange . Systematic investigation of labeling single chain or parts of a macromolecule has unveiled detailed structures of polymers.…”