Gutta. I. Single crystals of alpha‐gutta

Abstract

Gutta, the polyisoprene hydrocarbon obtained from gutta percha or balata, is usually considered to differ from rubber in that gutta is a trans‐isomer and rubber a cis‐isomer of polyisoprene. Most of the data on the basis of which these structures have been assigned come from x‐ray diffraction pictures of polycrystalline polymer. Single crystal data have not been published, although such data would provide more detailed information. Chicle gutta has been shown to be a lower molecular weight modification of gutta from gutta percha. As a consequence of its lower molecular weight chicle gutta is a granular, free‐flowing powder, whereas gutta percha gutta is horny and tends to clump together. Because of its physical characteristics and lower molecular weight, chicle gutta was used first in an attempt to grow single crystals of gutta. By working with dilute solutions, well‐shaped single crystals of chicle gutta as large as 0.35 mm. in the long direction were obtained. From gutta percha Pahang, crystals 0.10 mm. long were isolated. Crystals could be grown either by slow diffusion of solvent or by cooling a supersaturated solution. Crystals were found to be optically anis tropic and to exhibit parallel extinction when examined under crossed Nicols with the polarizing microscope. Crystals obtained were of the alpha modification of gutta.

Morphology and properties of trans-1,4-polyisoprene crystallized from solution

“…31 Also a decrease in crystallinity with decreasing molecular weight in the 5000-30 000 range was reported for trans- The noncrystalline component is expected to consist of chain folds, chain ends, interlamellar links, and intralamellar defects. Assuming intralamellar defects to be negligibly small, the noncrystalline fraction is given by16 FS = \UF+ C}/Nn (1) where U is the average number of monomer units per fold and interlamellar traverse combined, F is the number of folds and interlamellar traverses per chain with a number-average degree of polymerization of Nn, and C is the average number of monomer units in the two chain ends. The crystalline fraction, 1 -Fs, is related to the above parameters and to the crystalline stem length, Lc, by…”

Morphology of solution crystallized trans-1,4-polyisoprene

“…The d-spacings of most of the electron diffraction patterns, as calculated by Bragg's law, compared favourably with the orthorhombic unit cell of LMF given by Bunn [12]. Similar crystals of LMF, with excessive overgrowth, were obtained from n-dodecane [8] and benzene solutions [4]. Crystallization of TPIP-2 was found to be convenient in the temperature range of 23 ~ -33 ~ Hexagonal shaped platelets ( Fig.…”

Dielectric relaxation in lamellas of trans-1,4-polyisoprene and a block copolymer derivative

“…How-Figure 2. Dielectric loss versus temperature for -TPI lamellas: (a) filled squares, 1 Hz; open squares, 100 Hz; (b) filled triangles, 0.1 Hz; open triangles, 10 Hz; filled squares, 1 kHz. ever, the dielectric loss maxima for both processes are about an order of magnitude larger than those found for the TPI mat.…”