Cyclic Poly(4-methyl-1-pentene): Efficient Catalytic Synthesis of a Transparent Cyclic Polymer

Abstract

Cyclic polymers possess properties that are significantly different from their linear analogs, such as higher densities, smaller hydrodynamic volumes, and higher glass transition temperatures. Poly­(4-methyl-1-pentene) (PMP), a linear polyolefin, is a commercial transparent thermoplastic and has applications in packaging materials and release membranes. Polymerizing 4-methyl-1-pentyne with a tungsten alkylidyne catalyst and subsequent hydrogenation (>99%) provided cyclic poly­(4-methyl-1-pentene) ( c-PMP). Evidence of a cyclic topology comes from rheology/viscosity studies, light scattering measurements, and size-exclusion chromatography. Importantly, atactic c-PMP exhibits a T g (39 °C) 10 °C higher than the linear analog. A 15 g-scale cyclic polymerization was also achieved with 1-pentyne. Subsequent hydrogenation yielded 10 g of cyclic poly­(1-pentene). Measurements of initial rates during the polymerization of 1-pentyne reveal a catalyst activity of 180,000,000 g/molcat/h.

PolyDODT: a macrocyclic elastomer with unusual properties

“…This difference in time is due to the smaller hydrodynamic volumes that physically more compact cyclic polymers possess, which is consistently reported for cyclic polymers. 26,27 The R g and R h values and intrinsic viscosities of the cycles are also smaller than those of the linear samples of similar molecular weight and close to the theoretical expectation of g ≈ 0.66. 16,[28][29][30][31][32] Cyclic polymers are expected to have lower intrinsic viscosities than linear counterparts: theory suggests a ratio of g′ = [η cyclic ]/[η linear ] = 0.4-0.5.…”

Ultra-High-Molecular-Weight Macrocyclic Bottlebrushes via Post-Polymerization Modification of a Cyclic Polymer

“…Confirming a cyclic topology for cyclic polymers and producing them on a large scale is challenging. Though strong supporting evidence from size exclusion chromatography, dynamic light scattering, static light scattering, intrinsic viscosity, ozonolysis, and rheology clearly support a cyclic topology for polymers produced using our W-catalyst, ,, absolute evidence for the topology was missing. The AFM images presented herein for two different cyclic bottlebrushes and their size relationship with DP n , provide for the first time, absolute evidence for a cyclic topology.…”

“…To aid in comparing the cyclic architecture to a linear counterpart, linear PPA ( l -PPA ) was also synthesized using acetylacetonato­(1,5-cyclooctadiene) rhodium­(I) as the catalyst in THF at ambient temperature. , The resulting linear polymer was characterized by 1 H NMR spectroscopy (Figure S3) and GPC ( M n = 213 kDa and M w / M n = 1.68) (Figure S4). Evidence of the cyclic topology for the polymer prepared with the tungsten catalyst was obtained by two characteristic GPC plots. ,,,, When comparing the plot of log­(molar mass) versus elution time for c -PPA and l -PPA (Figure A), it was clear that at any point along the elugram that c -PPA eluted later than its linear counterpart of identical molecular weight. Moreover, the plot of log­(intrinsic viscosity) versus log­(molar mass) (Figure B) indicated a consistently lower intrinsic viscosity of c -PPA compared to its linear analog at a given molecular weight.…”

“…Cyclic bottlebrushes, on the other hand, have not been explored to this extent due, in part, to limitations in purity and synthetic challenges presented during their preparation. Ring-closing techniques of α- and ω-end groups to form cyclic polymers generate unavoidable linear impurities from competing intermolecular coupling. , Excitingly, recent developments in ring-expansion polymerization (REP) with ruthenium or tungsten-based catalysts enable the synthesis of pure cyclic polymers with excellent yields (>98%). ,− …”

Soluble Polymer Precursors via Ring-Expansion Metathesis Polymerization for the Synthesis of Cyclic Polyacetylene

“…Cyclic polyacetylene ( c -PA ) is now accessible from acetylene gas and catalyst 1 − (Figure E), but the relationships between its cyclic topology and physical, electronic, and mechanical properties are unknown. Smaller hydrodynamic volumes, lower intrinsic and melt viscosities, and higher glass transition temperatures ( T g ) are properties that differ between linear and cyclic polymers. ,− Potentially more conjugated, and therefore more conductive, cyclic polymers have fewer degrees of freedom due to their inherent topological constraint . However, previous studies have suggested more limited conjugation lengths for cyclic polymers that could arise from segment bending/torsion, possibly mitigating cyclic topology effects on conductivity. , Nevertheless, attributable to a low-energy isomerization barrier for the ring structure, c -PA contains >99% trans double bonds.…”