Microdomains in poly(4-methyl-1-pentene) single crystals

Abstract

It is shown that in a given single crystal of poly(4-methylpentene-l) (P4MP1) polymorph III there exist narrowly delimited microdomains that give rise to different electron diffraction patterns. These domains have the same crystallographic unit cell but opposite c axis (chain axis) orientation. Dark held electron microscope images show that the number, size, and shape of the microdomains vary from one crystal to another. The domain boundaries are usually perpendicular to one crystal edge. These effects are discussed in relation to twinning by merohedry.

A low symmetry structure of isotactic poly(4-methyl-pentene-1), Form II. An illustration of the impact of chain folding on polymer crystal structure and unit-cell symmetry

“…The structure derivation of Form II of P4MP1 parallels strikingly that of Form III due to De Rosa et al [7], even more so than the recent analyis of Form II [1], De Rosa et al [7] also had to discard models of Form III in which inappropriate combinations of clinicity/chirality of the four chains in the unit-cell did not fit the experimental single crystal electron diffraction pattern recorded by Charlet et al [5] and Pradère et al [8]. As seen in Fig.…”

“…Although Form III has a tetragonal cell, the twinned components differ by the clockwise or counter-clockwise rotation of the chains in the unit-cell relative to the a or b axes. Twinned single crystals of Form III were investigated by Pradère et al [8]. The monolayer, twinned single crystals are frequently multiple twins in which the twinned microsectors are bounded by (100) and/or (110) twin planes.…”

“…Charlet, Delmas and co-workers [5,6] established the existence of further crystal structures that are produced when P4MP1 is crystallized from various solvents, and using different concentrations, thermal histories, etc. De Rosa et al established (and later refined) the crystal structure of the Form III of P4MP1 [7] using X-ray powder diffraction and selected area electron diffraction data collected by Charlet et al [5] and Pradère et al [8] on single crystals of this form. Rastogi et al [9] explored the pressure-temperature phase diagram of bulk P4MP1 and confirmed the existence of a hexagonal or trigonal phase based on a 3 1 helix conformation, first proposed by Charlet and Delmas [6] and also analyzed by De Rosa [10].…”

A nonlocal model of fracture by crazing in polymers

“…A hint at the likely growth properties of WðF; ÁÞ is provided by observations of sharp twin interfaces in crystalline polymers deformed in shear (Agar et al, 1959;Reneker and Geil, 1960;Geil, 1963;Kiho et al, 1964;Keller, 1968;Kovacs et al, 1969;Wittmann and Kovacs, 1970;Pradère et al, 1988;Alcazar et al, 2006). Atomistic simulations of shear deformation in polymers also supply evidence of lamination and of the development of sharp interfaces (Fortunelli et al, 2004;Fortunelli and Ortiz, 2007).…”

A micromechanical damage and fracture model for polymers based on fractional strain-gradient elasticity

“…Conveniently, for purposes of optimal scaling only the growth properties of W (F , ·) are required. A hint of the likely growth properties of W (F , ·) is provided by observations of sharp twin interfaces in crystalline polymers deformed in shear (Agar et al, 1959;Reneker and Geil, 1960;Geil, 1963;Kiho et al, 1964;Keller, 1968;Kovacs et al, 1969;Wittmann and Kovacs, 1970;Pradère et al, 1988;Alcazar et al, 2006). Atomistic simulations of shear deformation in polymers also supply evidence of lamination and of the development of sharp interfaces (cf., e. g., Fortunelli et al (2004); Fortunelli and Ortiz (2007) and references therein).…”