Polymerization-Induced Nanostructural Transitions Driven by In Situ Polymer Grafting

Abstract

Polymerization-induced structural transitions have gained attention recently due to the ease of creating and modifying nanostructured materials with controlled morphologies and length scales. Here, we show that order–order and disorder–order nanostructural transitions are possible using in situ polymer grafting from the diblock polymer, poly­(styrene)-block-poly­(butadiene). In our approach, we are able to control the resulting nanostructure (lamellar, hexagonally packed cylinders, and disordered spheres) by changing the initial block polymer/monomer ratio. The nanostructural transition occurs by a grafting from mechanism in which poly­(styrene) chains are initiated from the poly­(butadiene) block via the creation of an allylic radical, which increases the overall molecular weight and the poly­(styrene) volume fraction. The work presented here highlights how the chemical process of converting standard linear diblock copolymers to grafted block polymers drives interesting and controllable polymerization-induced morphology transitions.

Controlling nanostructure and mechanical properties in triblock copolymer/monomer blends via reaction-induced phase transitions

“…Although synthetic improvements for controlling polymer topology and chemical composition have led to TPE advances, there are a wealth of opportunities in utilizing in situ reaction and processing modalities to tune macromolecular structures and nanoscale phases not easily accessible via traditional methods. [8][9][10][11] The molecular architecture of TPEs is based on a block polymer framework in which covalent bonds chemically link distinct repeat segments or ''blocks'' (e.g., A or B blocks in an ABA triblock copolymer) to form a single macromolecule. 12 Block polymers will microphase separate into distinct domains as a result of the incompatibility between the polymer blocks.…”

“…Our strategy follows previously published work in which PS is grafted from the PBD backbone of a PS-PBD diblock copolymer via the generation of an allylic radical. 9,10 The in situ grafting during the polymerization of styrene resulted in both order-order and disorder-order nanostructural transitions, 9,10 but the impact of these changes on properties was not previously investigated. The polymer grafting chemistry has been shown to be generalizable to other unsaturated polymer motifs (hybrid inorganic nanoparticle/polymer materials) and grafting polymers (PS and poly(methyl methacrylate)).…”

Simultaneous Reduction and Polymerization of Graphene Oxide/Styrene Mixtures To Create Polymer Nanocomposites with Tunable Dielectric Constants

“…29,30 For example, compared to conventional heating, the microwave-assisted synthesis of PS has been shown to reduce reaction times. 31,32 Furthermore, microwave-assisted polymer grafting on diblock copolymers to induce nanostructural transitions has recently been reported, 33 suggesting that the combination of nanoscale fillers with polymer materials using microwave reaction processes will lead to advances in the creation of nanostructured hybrid polymer materials. Therefore, the combination of microwave heating to simultaneously polymerize monomer and reduce GO has major benefits for rapidly producing RGO polymer nanocomposites.…”

“…Graphene-based polymer nanocomposite materials created using in situ polymerization procedures have been shown to increase graphene, RGO, and GO dispersion within polymer matrixes and lead to enhanced mechanical and electrical properties. ,,, One method in particular, microwave heating, to simultaneously reduce GO and synthesize polymers has been shown to be an efficient method for creating polymer nanocomposites with well-dispersed RGO. ,, Microwave heating has been broadly applied to many chemical reactions ranging from organic syntheses to polymerization because of increased product yields and reaction rates. , For example, compared to conventional heating, the microwave-assisted synthesis of PS has been shown to reduce reaction times. , Furthermore, microwave-assisted polymer grafting on diblock copolymers to induce nanostructural transitions has recently been reported, suggesting that the combination of nanoscale fillers with polymer materials using microwave reaction processes will lead to advances in the creation of nanostructured hybrid polymer materials. Therefore, the combination of microwave heating to simultaneously polymerize monomer and reduce GO has major benefits for rapidly producing RGO polymer nanocomposites.…”

Polymerization-Induced Microphase Separation with Long-Range Order in Melts of Gradient Copolymers

“…The structuring in bulk, which is often referred to as polymerization-induced phase separation (PIPS) or microphase separation (PIMS) [ 30 , 31 , 32 , 33 ], has been studied significantly less than PISA; moreover, the majority of works on this topic deal with structures obtained through kinetic arrest or cross-linking [ 31 ]. To the best of our knowledge, PIMS resulting in structures with long-range order has almost not been studied (there are examples of graft polymerization-induced [ 34 , 35 ] formation of such structures), and gradient copolymers, given the recent advances in PISA [ 28 , 29 ], seem to be an excellent candidate for further investigation in this area.…”