3D Single Cyclized Polymer Chain Structure from Controlled Polymerization of Multi-Vinyl Monomers: Beyond Flory–Stockmayer Theory

Abstract

Controlled/living radical polymerization (CRP) is a widely used technique that allows the synthesis of defined polymer architectures through precise control of molecular weights and distributions. However, the architectures of polymers prepared by the CRP techniques are limited to linear, cross-linked, and branched/dendritic structures. Here, we report the preparation of a new 3D single cyclized polymer chain structure from an in situ deactivation enhanced atom transfer radical polymerization of multivinyl monomers (MVMs), which are conventionally used for the production of branched/cross-linked polymeric materials as defined by P. Flory and W. Stockmayer nearly 70 years ago. We provide new evidence to demonstrate that it is possible to kinetically control both the macromolecular architecture and the critical gelling point in the polymerization of MVMs, suggesting the classical Flory-Stockmayer mean field theory should be supplemented with a new kinetic theory based on the space and instantaneous growth boundary concept.

Single Cyclized Molecule Versus Single Branched Molecule: A Simple and Efficient 3D “Knot” Polymer Structure for Nonviral Gene Delivery

“…We have recently discovered that it is no longer a formidable task to homopolymerize MVMs by controlled/living radical polymerization based on our so-termed "deactivation enhanced strategy". We have also introduced a new kinetic model to supplement F−S theory, termed the "Kinetic Theory", 22 which can be used to explain the ability to kinetically control the homopolymerization of EGDMA and the occurrence of intramolecular cyclization reactions. This theory brings the spatial proximity of reactants into consideration, allowing the prediction of conditions where the internal cyclization can occur.…”

“…Therefore, a new polymer architecture was being formed which predominantly consists of internal cyclization reactions, i.e., intramolecular cyclization within a polymer chain rather than the usual hyperbranching between polymer chains (intermolecular cross-linking). This newly fathomed polymer architecturesingle chains knotted upon themselves, is termed a "single cyclized" molecular structure, 22 in contrast to the "single branched" structure of dendrimers. As numerous reports in literature demonstrate that a higher transfection performance can be achieved through the branched architecture, it can be reasonably hypothesized that the new knotted structure of single cyclized polymer chains will out-perform currently available polymer structures in terms of efficacy, cell viability, and scalability.…”

Controlled multi-vinyl monomer homopolymerization through vinyl oligomer combination as a universal approach to hyperbranched architectures

“…Indeed, the inclusion of only small amounts of MVMs, if carried out in addition polymerizations, for example, free radical polymerization (FRP), will result in the formation of a macroscopic crosslinked network of MVMs. However, a deactivation-enhanced atom transfer radical polymerization (DE-ATRP) strategy can efficiently delay the gel point of the MVM homopolymerization up to 60% monomer conversion in a concentrated polymerization system [30][31][32] . By this approach, a Under the condition of a restricted growth boundary (small kinetic chain length), cyclized structures are formed through the strategy of intra-enhanced propagation.…”

“…1a). This discovery prompted us to develop a new model that gives a significant supplementation to the classical F-S theory based on the space and instantaneous growth boundary concept 30 . Most importantly, this study subverted the traditional impression of MVMs reactions-'uncontrolled and challenging'.…”

“…As aforementioned, we already investigated the case of favoured intramolecular events during MVMs homopolymerization, leading to single-cyclized polymers [30][31] . This led us to ask a further question: if the intramolecular reaction can be enhanced by the suppression of intermolecular reactions (leading to a cyclized polymer structure), how can the intermolecular reaction be facilitated with the suppression of intramolecular reactions?…”