State of order in isotactic polyhexylethylene

Abstract

Cooling slowly from the melt and annealing at 250 K for a month isotactic polyhexylethylene becomes partially crystalline. The degree of crystallinity, calculated according to the method of Hermans and Weidinger, is 0.3. The wide‐angle x‐ray diffraction diagram shows seven reflections, not completely independent of one another. These x‐ray data do not allow an exact determination of the structure. The main chins possibly form quaternary helices (e. g., 4/1 or 7/2 helices) and the side chains are arranged in triclinic structure. The unit cell may be monoclinic: a ∼ 0.56 nm, b ∼ 3.8 nm, c ∼ 0.76 nm (in case of a 4/1 helix), β ≃ 97° The melting temperature is 278 K and the heat of fusion amounts to 30 J/g.

Mechanistic Insight into the Stereoselective Cationic Polymerization of Vinyl Ethers

“…Despite the demonstration of a slightly higher level of isotacticity as chain length increased, a corresponding decrease in the melting temperature ( T m ) of the materials was observed (Figure A). This observation suggests that the conformational flexibility of the side chains has an impact on polymer crystallization within this series …”

“…This observation suggests that the conformational flexibility of the side chains has an impact on polymer crystallization within this series. 75 The steric properties of branched alkyl vinyl ether monomers demonstrated a pronounced influence on the stereoselectivity achieved with catalyst (R)-2 (Figure 8B). In order to probe these effects systematically, the site of branching was placed progressively closer to the ether through the evaluation of isoamyl vinyl ether (iAVE), iBVE, and isopropyl vinyl ether (iPVE).…”

Morphology of Poly(1-olefin)s from Poly(1-octene) to Poly(1-eicosene)

“…[3,5,11] The crystal structure of poly(1-tetradecene), poly(1-hexadecene), and poly(1-octadecene) of type II crystallites was already determined by Turner-Jones to be orthorhombic, the reflections in wide and small angle X-ray scattering experiments were labeled. [3] In addition, Trafara observed the same crystal structure for poly(1-docosene).…”

“…First reports on the crystallization behavior of isotactic poly(1-olefin)s with linear side chains of four to twenty C-atoms were provided in detail by Turner-Jones in 1964 [3] and some further investigations were done by Trafara et al [5,11] in the late '70s. They found in addition to the amorphous phase two possible crystalline modifications.…”

“…The long periods of poly(1-decene), and poly(1dodecene) in the modification I and the long period of poly(1-hexadecene) in the modification II are measured additionally to the other values known from Turner-Jones [3] and Trafara. [5,11] The determination of the amorphous halos in the wide and small angle regimes is simplified by using the atactic poly(1-dodecene). The measurements can be done at room temperature and a melting and/or quenching regime is not required.…”