Epoxy functionalized cycloolefin polymers by ring-opening metathesis polymerization

Functional COPs by ROMP and post-polymerization modification.

Role of Block Copolymers in Tissue Engineering Applications

Research on synthesis, characterization, and understanding of novel properties of nanomaterials has led researchers to exploit their potential applications. When compared to other nanotechnologies described in the literature, electrospinning has received significant interest due to its ability to synthesize novel nanostructures (such as nanofibers, nanorods, nanotubes, etc.) with distinctive properties such as high surface-to-volume ratio, porosity, various morphologies such as fibers, tubes, ribbons, mesoporous and coated structures, and so on. Various materials such as polymers, ceramics, and composites have been fabricated using the electrospinning technique. Among them, polymers, especially block copolymers, are one of the useful and niche systems studied recently owing to their unique and fascinating properties in both solution and solid state due to thermodynamic incompatibility of the blocks, that results in microphase separation. Morphology and mechanical properties of electrospun block copolymers are intensely influenced by quantity and length of soft and hard segments. They are one of the best studied systems to fit numerous applications due to a broad variety of properties they display upon varying the composition ratio and molecular weight of blocks. In this review, the synthesis, fundamentals, electrospinning, and tissue engineering application of block copolymers are highlighted.

Highly active ruthenium metathesis catalysts enabling ring-opening metathesis polymerization of cyclopentadiene at low temperatures

Development of versatile ruthenium olefin-metathesis catalysts with high activity, stability, and selectivity is a continuous challenge. Here we report highly controllable ruthenium catalysts using readily accessible and versatile N-vinylsulfonamides as carbene precursors. Catalyst initiation rates were controlled in a straightforward manner, from latent to fast initiating, through the facile modulation of the N-vinylsulfonamide ligands. Trifluoromethanesulfonamide-based catalysts initiated ultrarapidly even at temperatures as low as -60 °C and continuously propagated rapidly, enabling the enthalpically and entropically less-favored ring-opening metathesis polymerizations of low-strained functionalized cyclopentene derivatives, some of which are not accessible with previous olefin-metathesis catalysts. To our surprise, the developed catalysts facilitated the polymerization of cyclopentadiene (CPD), a feedstock that is easily and commonly obtainable through the steam cracking of naphtha, which has, to the best of our knowledge, not been previously achieved due to its low ring strain and facile dimerization even at low temperatures (below 0 °C).

Polypentenamer Renaissance: Challenges and Opportunities

This Viewpoint highlights the viability and increasing variety of functionalized polypentenamers as unique and valuable materials created through enthalpy-driven ring-opening metathesis polymerization (ROMP) of low ring strain cyclopentene monomers. The terms "low ring strain" and "enthalpy-driven" are typically conflicting ideologies for successful ROMP; however, these monomers possess a heightened sensitivity to reaction conditions, which may be leveraged in a number of ways to provide performance elastomers with good yield and precise functional topologies. Over the last several years, a rekindled interest in these systems has led to a renaissance of research aimed at improving their synthesis and exploring their potential. Their chemistry, applications, and future outlook are discussed.

Well-Defined and Precision-Grafted Bottlebrush Polypentenamers from Variable Temperature ROMP and ATRP

Polypentenamer macroinitiators are synthesized through variable temperature ring opening metathesis polymerization of 3-cyclopentenyl α-bromoisobutyrate, which has sufficient ring strain (ΔH_p = -22.6 kJ mol^-1) to produce targeted molar mass (<5% from theoretical), low dispersity (1.17 ≤ Đ ≤ 1.23), and high conversion (∼72%). An initiation site for atom-transfer radical polymerization at every fifth backbone carbon allows "grafting-from" of styrene with quantitative initiation and linear molar mass increase with time. These bottlebrushes retain a low dispersity (Đ ≤ 1.34) at varying graft degrees of polymerization (5 ≤ N_sc ≤ 49) and have a glass transition temperature highly sensitized to graft length. Extension of the grafts with methyl methacrylate produces a core-shell brush polymer with high molar mass (>1000 kg mol^-1) and Đ = 1.33. This system exhibits high synthetic versatility and control with a unique flexible backbone to expand the suite of densely grafted polymers.

Thioester functional polymers

Inspired by the uniqueness and ubiquity of thioesters in nature, much attention has been paid to thioester functionalized materials, yielding applications ranging from responsive polymers to bioconjugates and (bio)degradable polymers.

A new echelon of precision polypentenamers: highly isotactic branching on every five carbons

A systematic study shows that bulky allylic substituents on cyclopentene monomers affords a highly precise microstructure after ring-opening metathesis polymerization.