Spontaneous synthesis of a homogeneous thermoresponsive polymer network composed of polymers with a narrow molecular weight distribution

Abstract

We have developed a method to obtain a polymer gel consisting of a relatively homogeneous network structure composed of polymers with a narrow molecular weight simply by mixing the necessary compounds. In this method, a radical chain polymerization reaction with a fast reaction rate is combined with a radical addition cross-linking reaction that has a sufficiently slow reaction rate compared with the polymerization reaction. For the polymerization reaction, a multifunctional initiator with a strictly controlled number of polymerization initiation sites was used to prepare a star polymer with a chain number and length determined by living radical polymerization. In the cross-linking reaction, a multifunctional terminating agent was used to prepare a star polymer from a polymer with a narrow molecular weight via living radical polymerization followed by coupling with multiple polymer chains using a termination reaction. As a result, two kinds of reactions with greatly different kinetics occurred sequentially only when all of the compounds were mixed and allowed to stand at a constant temperature, and a relatively homogeneous network structure comprising cross-linked polymers with a low molecular weight distribution was inherently constructed.

Nonturbid Fast Temperature-Responsive Hydrogels with Homogeneous Three-Dimensional Networks by Two Types of Star Polymer Synthesis Methods

“…The reaction temperature was set to 4 °C, at which both NIPA and its polymer could be uniformly dissolved in the mixed solvent as reported in the previous work (Figure S1). ,− The monomer conversion was monitored using the consumption of the vinyl group of NIPA by 1 H NMR, and NIPA was smoothly consumed to reach 90% in approximately 1 h (Figure c).…”

“…Recently developed methods to synthesize polymers with precise structures have become applicable not only to research on single chains but also to the production of materials such as polymer gels. − Using an appropriate living or controlled radical polymerization, not only the network structure but also the arrangement of the monomers in the polymer chains constituting the network could be controlled. , Using such a polymer synthesis method that enables precise control, it is possible to construct a “functional polymer gel with a controlled monomer arrangement and polymer structure” that has not been obtained by conventional methods. Moreover, the preparation of such a functional polymer gel is possible by adding the required compounds in the appropriate order and in the required amount. ,,, …”

Application of pan-sharpening algorithm for correlative multimodal imaging using AFM-IR

“…37,38 There is spatial and physiochemical heterogeneity in the composition and organization of polymers in the plant cell wall that is impossible to replicate in a synthetic composite material. 39,40 This heterogeneity in the cell wall correlates with different mechanical properties across the cell, and this has bearing on whole-plant growth, cell morphogenesis, and development of tissues. 41,42 The intrinsic complexity of the cell wall confers a plant cell the ability to provide mechanical support and strength, yet also allow for growth and flexibility in challenging environmental conditions.…”

A Simple and Versatile Method for the Construction of Nearly Ideal Polymer Networks

“…Since PEG does not possess any active functional side groups, it has been impossible to incorporate further functionalities into the defect‐free gel networks, which limits the range of potential applications. There have been several reports on the synthesis of star polymer‐based gels other than PEG gels . Oshima and co‐workers synthesized a poly(acrylic acid) hydrogel by end‐linking two tetra‐arm poly( tert ‐butyl acrylate) units followed by the removal of the tert ‐butyl groups.…”

“…The hydrogel showed a higher shear modulus compared to that of the hydrogel formed by conventional random radical polymerization. Jochi and co‐workers reported the one‐pot synthesis of a poly( N ‐isopropylacrylamide) (PNIPAAM) gel by the polymerization of a tetra‐arm PNIPAAM followed by in situ end‐linking with a tetra‐functional crosslinker. Despite this effort directed at expanding the scope of the star‐polymer‐based approach for defect‐free gels, the reported synthetic methods suffer from either one or more of the following problems: 1) The method requires complex polymer end‐group modifications; 2) the end‐linking reaction does not proceed quantitatively, which leads to topological defects; and 3) the reaction rate cannot be controlled.…”