Günter Friedrich Schmidt

Structure and properties of poly(ethylene terephthalate) crystallized by annealing in the highly oriented state: 2. Melting behaviour and the mosaic block structure of the crystalline layers

Abstract The melting behaviour of drawn poly(ethylene terephthalate) bristles has been studied by means of differential scanning calorimetry. In addition the wide-angle X-ray diffraction pattern were analysed. For comparison some of the experiments were also carried out with undrawn samples. The differences in the melting curves of drawn and undrawn PET originate from the different crystallization kinetics. The density defect ( ϱ id c − ϱ∗ c ) between the ideal crystal density ϱidc and the effective density ϱ∗ c of the crystalline layers is a result of lattice vacancies introduced by the grain boundaries of the mosaic blocks. The relatively low ultimate crystallinity of PET is supposed to be caused by the hindrance of crystal growth of fibre direction during isothermal crystallization.

Über Zusammenhänge zwischen der Röntgenkleinwinkelstreuung und der morphologischen Struktur verstreckter Hochpolymerer

ZusammenfassungIn der vorliegenden Arbeit wird über Versuche berichtet, die Ergebnisse der Röntgenkleinwinkelstreuung an verstreckten Hochpolymeren mit Hilfe von elektronenmikroskopisch beobachtbaren Strukturen zu deuten. Geeignet behandelte elektronenmikroskopische Aufnahmen lassen sich als optische Gitter für Lichtbeugungsversuche verwenden. Die daran erhaltenen Lichtbeugungsdiagramme zeigen eine Intensitätsverteilung, die mit der röntgenographisch gemessenen gut übereinstimmt. Es ließ sich zeigen, daß die elektronenmikroskopisch an verschiedenen verstreckten Hochpolymeren (Polyäthylen, Polyoxymethylen und Polyäthylenterephthalat) gefundenen periodischen Querstrukturen nicht nur ihrem mittleren Abstand nach mit der röntgenographisch gefundenen Langperiode übereinstimmen, sondern daß sie auch die Intensitätsverteilung im Röntgenkleinwinkeldiagramm verständlich machen. Hieraus kann man den Schluß ziehen, daß die elektronenmikroskopisch beobachtete Oberflächenstruktur auch für das Innere massiver Proben als repräsentativ angesehen werden kann.SummaryExperiments reported in this paper pursued an explanation of X-ray small angle scattering of drawn polymers in terms of morphological structures being observed in the electron microscope. After appropriate treatment electron micrographs can be used as optical lattices for light scattering experiments.Diffraction patterns obtained in this manner show an intensity distribution which agrees quite well with that measured by X-rays. The striations observed electron-microscopically on the surface of various drawn polymers (PE, OPM, and PET) may explain the small angle X-ray pattern with respect to both long spacing and intensity distribution. So the surface structure observed by means of electron microscope is representative of the complete bulk sample.

Polymerization of eicosenoic acid and octadecyl fumarate in Langmuir-Blodgett multilayers

Abstract Langmuir-Blodgett multilayers of 2-eicosenoic acid and octadecyl fumarate were irradiated by ultra-violet (u.v.) light. The reaction was monitored by u.v. spectroscopy, and the photoproducts were isolated and identified to be polymers. The multilayers of both amphiphiles undergo substantial structural changes during polymerization, as observed by u.v. spectroscopy, small-angle X-ray scattering and scanning electron microscopy. The kinetics of the changes were investigated. The long-term stability and the thermal behaviour of monomeric and polymeric multilayers were studied as well. Partially polymerized samples underwent phase separation on storage. The melting of the multilayer structure was found to be partially reversible. Models for the different processes observed and their correlation are discussed.

Polymeric amphiphiles with hydrophilic main chain spacers: studies in monolayers and Langmuir-Blodgett multilayers

A methacrylic lipid was polymerized to form an amphiphilic homopolymer and random copolymers with various levels of acrylic acid comonomers. The behavior of these polymeric lipids was investigated in monolayers at the air-water interface and in Langmuir-Blodgett multilayers on polymer foil supports. The acrylic acid acts as a hydrophilic spacer along the polymer backbone, and improves the ability of the polymer to self-organize into highly ordered monolayers and ultimately LB multilayers. It is shown that the quality and stability of the multilayers increase substantially with the increase in comonomer content.