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

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.

Dissolution window in in situ polymerization preparation of polyamide single‐polymer composites

“…The nucleation of fibers is another important factor that affects the properties of SPCs because the identical chemical composition and highly oriented chains provide a high density of active nuclei. [ 33 ] In particular, in the approaches mentioned by Gurarslan and Tonelli, [ 34, 35 ] the nematic‐like microstructures of highly extended chains effectively nucleate the crystallization and provide superior reinforcement to the same polymer. The nucleation of fibers is also observed at the highest activator dosage in our study.…”

Prominent processing techniques to manipulate semiconducting polymer microstructures

“…498 More details on the role of inclusion compounds in the processing of bulk polymers can be found in other research articles and comprehensive literature reviews published by Tonelli and co-workers. [499][500][501][502][503][504]…”

Peering into the Kaleidoscope of Cyclodextrins

“…In polymer science, cyclodextrins can be used to include polymeric chains and template them into ordered and aligned forms that, after removal of the cyclodextrin, give rise to variants of the polymer materials with unique morphologies and improved thermal and mechanical properties [ 10 ].…”