Nanoscale Restructuring of Polymer Materials to Produce Single Polymer Composites and Miscible Blends.

Tonelli Tonelli

doi:10.3390/biom9060240

Abstract

I summarize work conducted in our laboratories over the past 30 years using small host molecules to restructure polymer materials at the nanometer level. Certain small molecules, such as the cyclic starches cyclodextrins (CDs) and urea (U) can form non-covalent crystalline inclusion compounds (ICs) with a range of guest molecules, including many polymers. In polymer-CD- and -U-ICs, guest polymer chains reside in narrow channels created by the host molecule crystals, where they are separated and highly extended. When the host crystalline lattice is carefully removed, the guest polymer chains coalesce into a bulk sample with an organization that is distinct from that normally produced from its melt or from solution. Amorphous regions of such coalesced polymer samples have a greater density, likely with less chain entanglement and more chain alignment. As a consequence, after cooling from their melts, coalesced amorphous polymers show glass-transition temperatures (Tgs) that are elevated above those of samples prepared from their solutions or melts. Upon cooling from their melts, coalesced samples of crystallizable polymers show dramatically-increased abilities to crystallize more rapidly and much closer to their melting temperatures (Tms). These unique behaviors of polymers coalesced from their CD- and U-ICs are unexpectedly resistant to extended annealing above their Tgs and Tms. Taking advantage of this behavior permits us to create polymer materials with unique and improved properties. Among these are amorphous polymers with elevated Tgs and semi-crystalline polymers with finer more uniform morphologies. Improved mechanical properties can be achieved through self-nucleation with small amounts of the same polymer made rapidly crystallizable through coalescence from its CD- or U-IC. This can lead to single polymer composites with as-received polymer matrices and self-nucleated reinforcements. Through simultaneous formation and subsequent coalescence from their common CD–ICs, stable well-mixed blends can be achieved between any two or more polymers, despite their inherent immiscibilities. Such coalesced and well-mixed blends are also resistant to phase segregation when heated for extensive periods well above their Tgs and Tms.

Highlights

For nearly 30 years, I have been interested in the non-covalently bonded inclusion compounds (ICs) formed between small host molecules and, in particular, their ICs formed with polymer guests [1].These polymer-ICs are not held together by chemical bonds [2]
U lattice is carefully removed from the common ICs, the included polymers are initially coalesced into well-mixed blends
The use of small host molecules to molecularly restructure polymer materials at the nanometer level were described here. Among such small molecule hosts, we focused on the cyclic starches CDs and U to form non-covalent crystalline ICs with a variety of polymers

Summary

Introduction

For nearly 30 years, I have been interested in the non-covalently bonded inclusion compounds (ICs) formed between small host molecules and, in particular, their ICs formed with polymer guests [1]. ICs, in addition to conformations having conformations and distinct from theirfrom bulk their samples may, [18], by the careful removal the hostofcrystalline lattice, be mobilities distinct bulk[18], samples may, by the carefulofremoval the host crystalline coalesced into bulkinto samples, which behave distinctly from bulk obtained from from their lattice, be coalesced bulk samples, which behave distinctly fromsamples bulk samples obtained solutions and melts [15,19,20,21,22]. Such coalesced amorphous and semi-crystalline polymers exhibit their solutions and melts and semi-crystalline polymers elevated glass-transion temperatures (T s)

Figures and

Compatible Coalesced Polymer Blends

Single Polymer Composites

Summary and Conclusions