Atsushi Noro

Design and properties of supramolecular polymer gels

Supramolecular polymer gels are precisely designed physical gels brought together by reversible secondary interactions to form three dimensional networks of melt macromolecules. Generally, they differ from supramolecular gels because they are comprised of polymers instead of low molecular weight compounds. Recently, much effort has focused on designing supramolecular polymer gels and related materials with excellent properties; indeed, improvements have been made in their supramolecular interactions, complementarity in the non-covalent bonding units, the nature of the macromolecular building blocks, and strand elasticity of supramolecular polymer networks. Owing to the precise molecular design, they represent nanophase separation and characteristic viscoelasticity. Here, we review supramolecular polymer gels in terms of molecular design, morphology, and rheology. We also discuss future directions in practical application of supramolecular polymer gels.

Simple preparation of supramolecular polymer gels viahydrogen bonding by blending two liquid polymers

Preparation of supramolecular polymer gels based on simple molecular design was demonstrated by blending carboxyl-terminated telechelic polymers and poly(ethyleneimine), where balance of an attractive force due to hydrogen bonding and a repulsive force induced by phase separation between polymers has been found as a key factor of supramolecular gelation.

Fabrication and Modification of Ordered Nanoporous Structures from Nanophase-Separated Block Copolymer/Metal Salt Hybrids

We report facile preparation of nanoporous thin films by rinsing out a metal salt from nanophase-separated hybrid films composed of a block copolymer and a water-soluble metal salt. Nanophase-separated hybrids were prepared by mixing polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) and iron(III) chloride in a solvent of pyridine, followed by solvent-casting and thermal-annealing. Film samples with a thickness of ca. 100 nm were fabricated from the nanophase-separated hybrids by using a microtoming technique. Metal salts in the films were removed by immersion into water to fabricate nanopores. Morphological observations were conducted by using transmission electron microscopy (TEM). Ordered cylindrical nanopores were clearly observed in the thin films prepared from the water-immersed hybrids which originally present cylindrical nanodomains. These nanoporous films were modified by loading another metal salt, samarium(III) nitrate, into the nanopores on the basis of the coordination ability of P4VP tethered to the pore walls. The samples after loading treatment were evaluated by TEM observation and elemental analysis with energy dispersive X-ray spectroscopy.

Highly Extensible Supramolecular Elastomers with Large Stress Generation Capability Originating from Multiple Hydrogen Bonds on the Long Soft Network Strands

Highly extensible supramolecular elastomers are prepared from ABA triblock-type copolymers bearing glassy end blocks and a long soft middle block with multiple hydrogen bonds. The copolymer used is polystyrene-b-[poly(butyl acrylate)-co-polyacrylamide]-b-polystyrene (S-Ba-S), which is synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Tensile tests reveal that the breaking elongation (εb ) increases with an increase in the middle block molecular weight (Mmiddle ). Especially, the largest S-Ba-S with Mmiddle of 3140k, which is synthesized via high-pressure RAFT polymerization, achieves εb of over 2000% with a maximum tensile stress of 3.6 MPa, while the control sample without any middle block hydrogen bonds, polystyrene-b-poly(butyl acrylate)-b-polystyrene with Mmiddle of 2780k, is merely a viscous material due to the large volume fraction of soft block. Thus, incorporation of hydrogen bonds into the large molecular weight soft middle block is found to be beneficial to prepare supramolecular elastomers attaining high extensibility and sufficiently large stress generation ability simultaneously. This outcome is probably due to concerted combination of entropic changes and internal potential energy changes originating from the dissociation of multiple hydrogen bonds by elongation.

Macromol. Rapid Commun. 8/2016

Back Cover: Highly extensible supramolecular elastomers with large stress generation ability can be prepared from large ABA triblock copolymers bearing hydrogen-bonded B soft block. The large stress is induced by extension of both network strands and hydrogen bonds on the strands while stress concentration at glassy domains is avoided by hydrogen bond breaking, attaining high extensibility. Further details can be found in the article by M. Hayashi,* A. Noro,* and Y. Matsushita on page 678.