Zur kristallstruktur der polycarbonate aus 4,4′-dihydroxydiphenyl-2,2-propan, 4,4′-dihydroxydiphenylsulfid und 4,4′-dihydroxydiphenylmethan†

TLDR: In this paper, the authors show that polycarbonate from 4,4′-dihydroxydiphenyl-2,2-propan has a high shear strength.

Abstract: Es wird gezeigt, das das Polycarbonat aus 4,4′-Dihydroxydiphenyl-2,2-propan monoklin in der Raumgruppe Cs2 mit je 4 Ketten in der Gitterzelle, das Polycarbonat aus 4,4′-Dihydroxydiphenylsulfid und das aus 4,4′-Dihydroxydiphenylmethan dagegen rhombisch in der Raumgrupe C2v9 mit je 2 Ketten in der Gitterzelle kristallisiert. Die Faseridentitatsperiode umfast in allen drei Substanzen jeweils zwei monomere Einheiten, so das je 8 bzw. je 4 monomere Einheiten in der Gitterzelle liegen. Die Kristalldichten sind 1,315 g/ccm fur das Polycarbonat aus 4,4′-Dihydroxydiphenyl-2,2-propan, 1,50 g/ccm fur das Polycarbonat aus 4,4′-Dihydroxydiphenylsulfid und 1,303 g/ccm fur das Polycarbonat aus 4,4′-Dihydroxydiphenylmethan. Die Faseridentitatsperioden der drei betrachteten Polycarbonate sind um ca. 15% bis 20% gegenuber ihrer theoretischen Maximallange bei voll ausgestreckten Ketten verkurzt. Dementsprechend betragt der Kristall-Elastizitatsmodul in Kettenrichtung ca. 450 bis 600 kp/mm2. Die betrachteten Kristallstrukturen enthalten keinerlei Gleitebenen, so das die Kristallbereiche eine hohe Scherfestigkeit besitzen. Die geringe Kristallisationstendenz des Polycarbonates aus 4,4′-Dihydroxydiphenyl-2,2-propan findet durch die Kristallstruktur eine plausible, zwanglose Erklarung. The polycarbonate from 4,4′-dihydroxydiphenyl-2,2-propane crystallizes monoclinically in the space group Cs2 with four chains each in the lattice cell, but the polycarbonate from 4,4′-dihydroxydiphenyl sulfide and from 4,4′-dihydroxydiphenyl methane crystallizes orthorhombically in the space group C2v9 with two chains each in the lattice cell. In all three substances, the fibre identity period always comprises two monomeric units, so that always eight and always four monomeric units, respectively, are located in the lattice cell. The crystal densities are 1.315 g./ccm. for the polycarbonate from 4,4′-dihydroxydiphenyl-2,2-propane, 1.50 g./ccm. for the polycarbonate from 4,4′-dihydroxydiphenyl sulfide, and 1.303 g./ccm. for the polycarbonate from 4,4′-dihydroxydiphenyl methane. The fibre identity period of the three substances, as compared with their theoretical maximum length in the case of fully stretched chains, has been shortened by 15 per cent to 20 per cent. Accordingly, the crystal elasticity modulus in the direction of the chain only amounts to about 450 to 600 kp./mm2. The crystal structures considered do not contain any glide planes, so that the crystal domains possess a high shear strength. The low crystallization tendency of the polycarbonate from 4,4′-dihydroxydiphenyl-2,2-propane is easily and plausibly accounted for by its crystal structure.