Crystallization of Defect-Free Polyethylene within Block Copolymer Mesophases

Abstract

We report the morphology and orientation of the crystals which form within the microdomain structures of diblock copolymers of linear polyethylene and glassy poly(vinylcyclohexane), LPE/ PVCH, across the spherical, cylindrical, and lamellar morphologies. Compared with short-branched polyethylene (such as hydrogenated polybutadiene), confinement of LPE within spheres, within cylinders, or between PVCH cylinders directly limits the crystal thickness and thereby the crystal melting point. Conversely, crystals formed within LPE lamellae are stacked orthogonally to the LPE/PVCH microdomain layering, so there is no direct limitation imposed on crystal thickness by confinement. As with LPE homopolymer, LPE crystals within lamellae thicken when annealed below the melting point, ultimately forming crystals whose thickness is significantly larger than their lateral extent, set by the bounding PVCH layers. The ribbon-like crystals which form within LPE cylinders or lamellae have a strong orientational coupling to the microdomains; prealignment of the cylindrical or lamellar mesophase by extensional flow yields macroscopic specimens with pronounced b-axial and a-axial orientations, respectively, after subsequent quiescent crystallization.

The crystal–crystal transition in hydrogenated ring‐opened polynorbornenes: Tacticity, crystal thickening, and alignment

“…For oriented specimens, two‐dimensional (2D) SAXS and WAXS measurements were conducted. 2D SAXS measurements used a custom‐designed Molecular Metrology (Northampton, MA; now Rigaku USA) point‐focusing X‐ray system,29 including a 2D multiwire detector. 2D WAXS measurements used a Statton pinhole camera system,30 using Kodak image plates read by a GE Biosciences Storm 820 scanner.…”

Crystallization of polymer chains confined in nanodomains

“…Consequently, the crystalline block crystallizes within hard (or glassy) nanodomains to form crystalline microdomain structures [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. It is generally observed for the crystallization in hard nanodomains that the melting temperature is considerably low and the final crystallinity is extremely small as compared with the case in the crystalline lamellar morphology formed by break-out crystallization (Fig.…”

A general mechanism for controlling thin film structures in all-conjugated block copolymer:fullerene blends

“…When one or both blocks of a diblock copolymer are semicrystalline, the kinetics of equilibrium phase separation compete with crystallisation [6][7][8] . Careful selection of the processing conditions can result in polymer crystals that are confined within the domains of the copolymer nanostructure [9][10][11][12][13] .…”

“…The diblock copolymer is symmetric and forms a lamellar nanophase separated structure, found to enhance polymer crystallisation relative to morphologies with higher curvature (e.g. cylinders or microemulsions) 10 . Only the P3HT block can crystallise, and PCBM cannot intercalate into the pure phase polymer crystal 14,15 .…”