Polymerization of lactams, 38. Copolymerization of 6-caprolactam with some of its non-homopolymerizing derivatives

It was demonstrated that non-homopolymerizing derivatives of 6-caprolactam: 7-cyclohexyl-1-aza-2-cycloheptanone (I) and 7-isopropyl-5-methyl-1-aza-2-cycloheptanone (II) were polymerizing with 6-caprolactam under conditions of the socalled hydrolytic polymerization. With its increasing content in the initial reaction mixture the copolymerization rate, the equilibrium content of the copolymer, and the reduced viscosity decreased. Lactam (I) was a more reactive comonomer in comparison with lactam (II).     

Antioxidantien und Stabilisatoren XXVIII. Gelchromatographie nichtflüchtiger phenolischer antioxidantien zur stabilisierung von polymeren

High resolution gel chromatography was applied to the analysis of phenolic antioxidants mixtures formed by an alkylation of 4,4'-isopropylidenebisphenol and used for the stabilisation of polyolefins and rubbers. The calibration by pure model substances provided values of relative zone rates on S-GEL-832 for a series of tert-butyl and tert-octyl derivatives of phenol and 4,4'-isopropylidenebisphenol. The chromatograms show in some cases a separation of isomers differing in size of their molecules in solution.     

Analytical study of the additives system in polyethylene

On the basis of standards of identification of substances in the additive system of polyethylene has been performed. Different methods for separation such as adsorption thin-layer chromatography, high-performance liquid chromatography with chemically bounded phases, and gas chromatography have been used. The fir al identification has been made with mass spectrometry. The substances have been extracted from polyethylene with hexane and chloroform.     

Determination of micromechanical properties of a hen’s eggshell by means of nanoindentation

The work describes the suitability and applicability of the nanoindentation method for the determination of the micromechanical properties of a hen’s eggshell. The values of elastic modulus E were monitored in five different locations along the eggshell’s meridian line. Detailed maps of elastic moduli at particular eggshell cross-sections revealed high variations in local values of E-moduli at individual points, but not significant differences of their means at distant parts of the eggshell. Mean values of E-modulus in different meridian positions did not vary significantly and ranged from 47.4 to 53 GPa. Experimental histograms were created of all elastic moduli showing the frequency of their occurrence and these revealed a rather high variation in E-moduli throughout the cross-section. The probability density function can be characterised by a symmetrical shape and the distribution of E-moduli can be approximated with the Gauss distribution. The nanoindentation technique proved to be a suitable, easy-to-use, and powerful tool for assessing local variations of the mechanical properties of hen’s eggshells.     

The putative Saginaw impact structure,Michigan, Lake Huron,in the light of gravity aspects derived from recent EIGEN 6C4 gravity field model

The hypothetical impact structure in the Saginaw Bay (Michigan, USA, Lake Huron) has been tested by the gravity data derived from the recent gravity field model EIGEN 6C4 (expanded to degree and order 2190, with ground resolution of ~9?km). The following gravity field aspects were used: the gravity disturbances/anomalies, second derivatives of the disturbing potential (Marussi tensor), two of three gravity invariants, their specific ratio (known as 2D factor), the strike angles, and the virtual deformations. These gravity aspects are sensitive in various ways to the underground density contrasts. For the Saginaw Bay area, we confirm that we do not see any typical impact crater in terms of gravity disturbance or the radial second order derivative, possibly because of the thick layer of the ice located at the place and time of the impact. But the “combed” strike angles (one type of the gravity aspects we use) disclose a trace of high pressure to the SE/S/SW of the Bay and may be due to an impacting body. Thus, we provide circumstantial evidence of the Younger Dryas impact hypothesis.     

Phase transition in swollen gels

Summary The photoelastic behaviour of two networks — polyacrylamide (PAAm) and of a network prepared by the copolymerization of acrylamide with 5 mol.% sodium methacrylate — was investigated in water-acetone mixtures. For the PAAm network the dependence of all photoelastic characteristics on the composition of the mixture is continuous. At 54 vol.% acetone in the mixture, the ionized network undergoes a transition which gives rise to jumpwise changes in the shear modulus, deformational-optical coefficient, C, and in the refractive index of the gel, n_g. While in the collapsed state the optical anisotropy of the statistical segment is negative, –3×10^–24 cm³ (indicating an interaction between the side chains), in the expanded state it is positive, 0.5 × 10^–24 cm³. The dependence of all optical characteristics on the composition of the mixtures suggests that: (a) in both networks we have a transition between two conformational states of the chain; while for the ionized network the transition is a discrete one, for the nonionized network it takes place in the range between 30 and 45 vol.% acetone in the mixture; (b) in both networks the gels are optically homogeneous throughout the whole range of compositions of the mixtures (and thus also in the close vicinity of the collapse of the ionized network).     

The participation of crown ethers in the initiation of group-transfer polymerisation

Summary The use of crown ethers in conjunction with alkali metal salts, as catalysts in group-transfer polymerization, is discussed.