# Free Volume Space of Polymers as a New Functional Nanospace: Synthesis of Guest Polymers

## TL;DR

This paper introduces free volume spaces in polymers as a new nanospace for synthesizing conductive polymers, leading to improved material properties.

## Contribution

The novelty is using polymer free volume as a functional nanospace for in-situ synthesis of conductive polymers.

## Key findings

- Conductive polymers like polypyrrole were successfully synthesized in the free volume of resins and rubbers.
- The composites showed enhanced mechanical and gas barrier properties.
- Rubber composites with polypyrrole acted as flexible mechanical-stress sensors.

## Abstract

Nanospace has been used as a specific field for syntheses and assemblies of molecules, polymers, and materials. Free volume space among polymer chains is related to their properties, such as permeation of gas and small molecules. However, the void has not been used as a functional nanospace in previous works. The present work shows synthesis of guest conductive polymers in free volume space of conventional synthetic resins and rubbers as a new nanospace. Vapor of heteroaromatic monomer and oxidative agent is diffused into the soft dynamic nanospace among the polymer chains under ambient pressure at low temperature. The oxidative polymerization provides the conductive polymers, such as polypyrrole (PPy), in the free volume space of poly(methyl methacrylate) (PMMA), polypropylene (PP), silicone rubber (SR), and polyurethane rubber (PU). The ratio of the free volume decreases with the infiltration of the conductive polymers. The composites exhibit the improved mechanical and gas barrier properties. The rubbers containing PPy are used as mechanical‐stress sensors with both the conductivity and flexibility. The free volume space of resins and rubbers can be used as a new dynamic nanospace for synthesis of functional polymer composites.

A new functional nanospace has been found in conventional synthetic resins and rubbers. Free volume, nanoscale pore among polymer chains, is used as a reaction field for synthesis of conductive polymers. Functional composites with enhanced performances, such as mechanical, gas barrier, and conductive properties, are developed by the infiltration of the guest conjugated polymers in the free volume space.