Cyclic Poly(4-methyl-1-pentene): Efficient Catalytic Synthesis of a Transparent Cyclic Polymer
Zhihui Miao, Digvijayee Pal, Weijia Niu, Tomohiro Kubo, Brent S. Sumerlin, Adam S. Veige
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 Tg (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.