Substituent Effects on Torsional Strain in Cyclopentene Derivatives: A Computational Study.

Density functional theory calculations were used to create a library of ring strain energies (RSEs) for 73 cyclopentene derivatives with potential use as monomers for ring-opening metathesis polymerization (ROMP). An overarching goal was to probe how substituent choice may influence torsional strain, which is the driving force for ROMP and one of the most understudied types of RSEs. Potential trends investigated include substituent location, size, electronegativity, hybridization, and steric bulk.

Ring-Opening Metathesis Polymerization of δ-Pinene: Well-Defined Polyolefins from Pine Sap.

Well-controlled ring-opening metathesis polymerization (ROMP) of δ-pinene is reported. The monomer is produced through a facile, metal-free, three-step synthesis from highly abundant and sustainable α-pinene. Using Grubbs third-generation catalyst, δ-pinene undergoes ROMP to high conversion (>95%) with molar mass up to 70 kg mol and narrow dispersity (<1.

Depolymerization of Bottlebrush Polypentenamers and Their Macromolecular Metamorphosis.

The depolymerization of bottlebrush (BB) polymers with varying lengths of polycyclopentene (PCP) backbone and polystyrene (PS) grafts is investigated. In all cases, ring closing metathesis (RCM) depolymerization of the PCP BB backbone appears to occur through an end-to-end depolymerization mechanism as evidenced by size exclusion chromatography. Investigation on the RCM depolymerization of linear PCP reveals a more random chain degradation process.

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.

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 (Δ = -22.6 kJ mol) to produce targeted molar mass (<5% from theoretical), low dispersity (1.17 ≤ ≤ 1.

Precision Polyelectrolytes with Phenylsulfonic Acid Branches at Every Five Carbons.

A precision polyethylene containing phenyl branches at every fifth carbon (p5Ph) is nearly quantitatively functionalized (≈95%) with sulfonic acid groups on the para-position of each phenyl branch (p5PhS-H). Unlike polystyrene sulfonate (PSS), p5PhS-H has a glass transition temperature (T = 109 °C) well below its thermal decomposition temperature (T ≈ 200 °C), making this new material capable of thermal processing into molds and films at temperatures between these thermal limits. Neutralization of the sulfonic acid groups with varying counter cations (Li , Na , Cs ) produces a new class of precision polyelectrolytes.

A Precision Ethylene-Styrene Copolymer with High Styrene Content from Ring-Opening Metathesis Polymerization of 4-Phenylcyclopentene.

Ring-opening metathesis polymerization of 4-phenylcyclopentene is investigated for the first time under various conditions. Thermodynamic analysis reveals a polymerization enthalpy and entropy sufficient for high molar mass and conversions at lower temperatures. In one example, neat polymerization using Hoveyda-Grubbs second generation catalyst at -15 °C yields 81% conversion to poly(4-phenylcyclopentene) (P4PCP) with a number average molar mass of 151 kg mol(-1) and dispersity of 1.

Rheological Evidence of Composition Fluctuations in an Unentangled Diblock Copolymer Melt near the Order-Disorder Transition.

Rheological and small-angle X-ray scattering (SAXS) measurements were conducted on a symmetric, low molar mass ( = 17.6 kg/mol), poly(-butylstyrene--methyl methacrylate) (PtBS-PMMA) diblock copolymer near the order-disorder transition temperature ( = 193 ± 1 °C). Evidence of composition fluctuations is apparent in the low frequency elastic (G') and loss (G″) moduli and in the temperature dependence of the peak scattering intensity, (*), up to 50 °C above the .