bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of surface physics techniques to surface coatings
Authors: Paterson P. J. K. , Moon A. R. , Aubert R. , Brooker K. , Kottek P. , Starbuck P. , Viglione G. , Willmott M. , Dean M. , Coates R. , Lubbock F. J. 
Published: June 2010

AbstractThis paper presents a review of aspects of surface coatings investigated at the Applied Physics Department, Royal Melbourne Institute of Technology, in consultation with Dulux (Australia). The major aim for Applied Physics is the application of surface physics techniques to the development of surface coatings. The principal techniques include scanning and transmission electron microscopy, optical microscopy, microprobe analysis, spectrophotometry, depthcomposition profiling by Auger spectroscopy, and ion‐beam erosion. The major surface‐coating projects have been: (a) development of white paint without pigment in which water emulsions were used to provide air bubbles to replace pigment as light‐scattering centers with the aim of finding the system with best optical and physical properties; (b) surface defects in paint films: a number of defects have been investigated, including overspray cratering, loss of gloss by microcracking, and change of color by the action of Benard Cells in high solids paint films; (c) the mechanism of marking of flat plastic interior paints when wiped; and (d) adhesion between coating and substrate: several surface coating‐substrate combinations are being examined by Auger spectroscopy and ion‐beam erosion.
1,3‐asymmetric induction in stereoregular radical reactions
Authors: Englin B. 
Published: June 2010

AbstractThe radical telomerization reactions of vinyl chloride or propylene with halomethanes were chosen as stereochemical models for studying the mechanism of stereoregular polymerization of the monomers.Conformational 1H‐NMR analysis was used to assign the relative configurations of the racemic diad and triad telomer forms. The assignment was based on comparisons of the CH2‐proton geminal shifts in molecular fragments ‐CHX‐CH2‐CHX‐ and rotational equilibria of the racemic forms measured by NMR spectroscopy over a wide temperature range in solvents with different dielectric and magneto‐anisotropic properties. Complete iterative analysis of 1H‐NMR spectra at 60 and 90 MHz was carried out by using the INDOR technique and the 1H‐{D} spectra of partially deuterated model compounds, synthesized from various mono‐ and dideuterosubstituted vinyl chlorides.Statistical treatment of the distribution of the diad and triad forms allowed the stereochemical course of the propagating reactions of the 1,3‐substituted vinylic radicals to be determined at temperatures ranging from 55 to 200°C and pressures up to 8000 kg/cm2. From these statistical data and the conformational equilibria of the racemic diastereomeric forms, it was revealed that the stereoregularity of the studied and probably similar reactions with 1,3‐substituted vinylic radicals may be ascribed predominantly to the effect of the γ‐substituent. A dynamic model of a 1,3‐asymmetric induction and the mechanism of conformational control in stereoregular free‐radical polymerization is discussed.
Copolymerization of styrene and methyl methacrylate photosensitized by a methyl methacrylate‐triethylaluminium complex
Authors: Allen P. E. M. , Chiaramonte P. , Hunter L. J. , Mair C. , Williams E. H. 
Published: June 2010

AbstractWe have re‐examined the copolymerization of methyl methacrylate (MMA) and styrene in the presence of triethylaluminium at 273°K under visible light following recent claims that it was an alternating system. We applied gel‐permeation chromatography to establish that the polymers had monomodal distributions and could be regarded as coherent samples for analysis. Proton and 13C‐NMR spectroscopy were used to determine the composition and structure of the copolymers and investigate the presence of complexes in the comonomer solutions. We found that the polymers produced are not strictly alternating. In the absence of excess, uncomplexed MMA, the system is a radical copolymerization of styrene and a 1:1 MMA‐AlEt3 complex with reactivity ratios such that there is a strong tendency for styrene (S) and MMA (M) units to alternate. The alternating SMS triads were predominantly isotactic. Significant proportions of SSS, MMM and MMS triads could be detected.
ESR studies of degradation in polymers. I. γ‐irradiation of poly(styrene‐co‐methyl methacrylate) at 77°k
Authors: O'Donnell J. H. , Pomery P. J. 
Published: June 2010

AbstractThe ESR spectra, due to trapped radicals produced by γ‐irradiation at 77°K, of random copolymers of styrene and methyl methacrylate of known composition and of the two parent homopolymers have been studied at 77°K. The yields of trapped radicals in the polymers were measured at several doses by double integration of the ESR spectra, and the G values for the production of radicals were calculated. The G(R) value for poly(methyl methacrylate) was calculated as 0.58 ± 0.2 and that for polystyrene as 0.05 ± 0.02. The variation of G(R) is not linear with polymer composition and is explained by a protective effect of the aromatic component resulting from energy transfer. Other chemical reactions and scavenging effects can be eliminated by consideration of the results from the analysis of the ESR spectra of the copolymers in terms of the homopolymers. It appears that different transfer mechanisms become operable as the copolymers are warmed up after irradiation at 77°K.
Use of mono‐ and multifunctional oxocarbenium salts in the polymerization of tetrahydrofuran
Authors: Franta E. , Reibel L. , Lehmann J. , Penczek S. 
Published: June 2010

AbstractOxocarbenium ions associated to a stable counterion SbF6− were used to initiate the polymerization of tetrahydrofuran; mono‐, di‐, and trifunctional initiators were prepared. They proceed by addition onto the monomer with formation of an ester group and react quantitatively; initiation by the mono‐ and di‐functional salts is rapid. This kind of derivative was used in order to prepare block and graft copolymers of controlled structure.
New catalyst systems for the polymerization of isobutylene at “high” temperature based on dialkylaluminum halides and electron‐acceptor molecules
Authors: Cesca S. , Priola A. , Ferraris G. , Busetto C. , Bruzzone M. 
Published: June 2010

AbstractCatalyst systems based on dialkylaluminum halides and electron acceptors, e.g., chloranil (CA), 1,3,5‐trinitrobenzene, 2,4,5,7‐tetranitrofluoren‐9‐one, etc., succeed in polymerizing isobutylene and co‐polymerizing it with isoprene to very high molecular weight products. The system Et2AlCl–CA was investigated in detail by studying the products resulting from the interaction of the components in the presence of monomer or of its model compounds, e.g., 2,4,4‐trimethyl‐1‐pentene or 1,1‐diphenylethylene, and also in their absence. The carbonyl group is the preferred site of attack by R2AlCl leading to hydroquinone derivatives, but the chlorine atoms of CA are not reactive under the conditions adopted. No relevant interactions between isobutylene and CA were evident by ultraviolet spectroscopy, whereas ESR investigations succeeded in detecting a clear signal at g = 2.005 lacking hyperfine structure and assigned to a semiquinone radical of CA. This paramagnetic species is quenched in the presence of isobutylene which is believed to be transformed into a radical‐cation species. A bicationic propagation mechanism, resulting from the coupling of the olefin radical‐cation, seems supported by the identification of 1,1,4,4‐tetraphenylbutadiene among the dimers of a model compound obtained under polymerization conditions.
Radiation‐ and photoinduced ionic polymerization
Authors: Hayashi Koichiro , Irie Masahiro , Yamamoto Yukio 
Published: June 2010

AbstractPhotoinduced polymerizations of α‐methylstyrene and styrene were carried out in the presence of electron acceptors. These polymerizations are proved to be initiated by radical, ion‐pair, or free ion formed through the photoexcited electron donor‐acceptor complex.Radiation‐induced cationic polymerizations of styrene and α‐methylstyrene were found to proceed by free cationic propagation. The effect of added electron acceptors in these polymerizations was investigated. The role of ion‐pair in radiation‐induced cationic polymerization is investigated by the use of optical absorption method at 77°K and pulse‐radiolysis technique at room temperature.
The relation between thermal decomposition of polymers and free radical formation under high vacuum pyrolysis
Authors: Tkáč A. 
Published: June 2010

AbstractThe fragments of the thermal decomposition of polymers (240–350°C) are hot free radicals and biradicals that after volatilization under vacuum can be trapped on the surface of a rotating cryostat (−195°C). The reactivity of these radicals is studied in the temperature range of −170 to 0°C by means of electron spin resonance. The rate of reactive radicals formation seems to be the primary process on which the burning and inflammation properties of the polymers depend.
Influence of polymer structures on the rate constants of ultrasonic degradation in diluted solutions
Authors: Lueb H. A. , Schoon Th. G. F. 
Published: June 2010

AbstractIt was shown that polymers with a lower activation energy for thermal degradation (polystyrenes) are degraded faster by progressive periods of irradiation than those with higher activation energies (polybutadienes). Furthermore a connection is assumed between the degradation velocity and the effective rheological diameter of the tertiary units or the limiting molecular weights achieved with the standard mechanical degradation process. In addition, the value of the second virial coefficient, determined by the slope mo of the straight line in the graph ζ/c related to c, is relevant for the degradation velocity. The polymers with the largest second virial coefficient show the fastest degradation velocity constant K1, according to which it could be assumed that with the increase in interactions between solvent and soluted polymer, the degradation is accelerated.
Study of the effect of 2,4,6‐trisubstituted phenols on the theromoxidative stability of polypropylene by the chemiluminescence method
Authors: Matisová‐Rychlá L. , Ambrovič P. , Kulíčková N. , Rychlý J. , Holčík J. 
Published: June 2010

AbstractThe chemiluminescence method was used for the study of thermooxidation of polypropylene. An attempt was made to interpret the time‐reaction relationship of chemiluminescence. The influence of 2,4,6‐trisubstituted phenols containing different substituents on the course of polypropylene thermooxidation is also discussed.
Antioxidative properties of phenyl‐substituted phenols. III. Model studies of synergistic actions between primary and secondary antioxidants
Authors: De Jonge C. R. H. I. , Van Der Maeden F. P. B. , Biemond M. E. F. , Huysmans W. G. B. , Mijs W. J. 
Published: June 2010

AbstractProducts originating from the action of primary and secondary antioxidants can account, after interaction, for the synergistic effects observed in some polymers, e.g., polypropylene. Marked synergistic actions were observed between 4‐alkoxy‐2,6‐diphenylphenols and β,β′‐disubstituted diethyl sulfides. Using the corresponding phenoxyl radicals and sulfoxides as the model compounds, several products arise and disappear.In the case of 4‐methoxy‐2,6‐diphenylphenoxyl and β,β′‐diphenyldiethyl sulfoxide, 4‐methoxy‐2,6‐diphenylphenol (the primary antioxidant) and the formation of a variety of sulfur compounds, capable of acting as peroxide decomposers, were detected, isolated, and identified using high‐pressure liquid chromatography (HPLC) as a separation technique followed by semipreparative isolation.
Intramolecular proton transfer in ortho hydroxybenzophenones
Authors: Klöpffer Walter 
Published: June 2010

AbstractThe photostability of UV stabilizers of the ortho hydroxybenzophenone type is discussed in terms of excited state proton transfer and radiationless transitions in the “phenol” and “quinone” tautomers. The first triplet state of the phenol form derived by quenching experiments is located between 22,000 and 20,090 cm−1. These limits of T1, together with published acidity data, suggest a deactivation cascade involving the triplet states. Nevertheless, very fast internal conversion cannot yet be ruled out as an alternative explanation for the high photostability of these materials.
Antioxidants and stabilizers. LXIII. Sensitized photooxidation of 2,2′‐methylenebis(4‐methyl‐6‐tert‐butylphenol)
Authors: Taimr L. , Pospišil J. 
Published: June 2010

AbstractThe photooxidation of 2,2′‐methylenebis (4‐methyl‐6‐tert‐butylphenol) (II) sensitized with methylene blue in methanol was investigated. The course of reaction is strongly influenced by the concentration of sensitizer and substrate. At a low concentration of methylene blue, bisphenol II is oxidized with singlet oxygen with the formation of hydroperoxide III, which is further oxidized to yield a mixture of diastereomeric hydroperoxides IVa and IVb. By raising the concentration of methylene blue this reaction is suppressed and bisphenol II is oxidized via the respective aryloxyl radicals gradually to methoxy derivatives VI, VII, and other products. Bisphenol II used in high concentration inhibits both the oxidation of bisphenol itself and that of other substrates. The effect can be compared with that of 1,4‐diazabicyclo(2,2,2)octane. The thermal decomposition of hydroperoxides III, IVa, and IVb leads to the regeneration of bisphenol II. The results provide a deeper insight into the knowledge of the formation of transformation products of antioxidants under the conditions of aging of polymers.
Antioxidants and stabilizers. LXI. Photochemical behavior of transformation products of phenolic antioxidants: 4‐tert‐butylperoxy‐2,5‐cyclohexadienone
Authors: Lerchová J. , Kotulák L. , Rotschová J. , Pilař J. , Pospíšil J. 
Published: June 2010

AbstractThe decomposition of 2,6‐di‐tert‐butyl‐4‐methyl‐4tert‐butylperoxy‐2,5‐cyclohexadienone (I) in n‐heptane solution irradiated with light having wavelengths of 333 nm and 436 nm and in the solid phase irradiated with solar light was investigated. The composition of the reaction mixture was studied by UV and IR spectrometry and chromatographically (gel permeation, thin layer). The radical species was recorded using the electron pulse resonance (EPR) method.
Specificity of the soled phase oxidation of polyolefins
Authors: Buchachenko A. L. 
Published: June 2010

AbstractThe kinetics and mechanism of elementary chemical reactions in solid polymers are reviewed. The activation energies and pre‐exponential factors of propagation and recombination rate constants are analyzed. The mechanism of hydroperoxide decomposition and chain branching are critically considered and the influence of oxygen on the chain branching probability is discussed. Some other problems of solid polymer oxidation are also discussed.
Morphology and mutual dependence of lamellas in bulk and oriented linear high polymer samples
Authors: Point J. J. 
Published: June 2010

AbstractThis paper discusses the morphology of individual lamellar crystals of semicrystalline linear high polymers in the bulk or oriented states. We discuss the simple two‐phase model, the model where the folds are level, and intermediate models. We also discuss the dependence of lamellas upon each other caused by the chains and fibrils which connect the crystals and the coalescence of the disordered parts of the lamellas.
Phase diagrams and pulse‐induced critical scattering
Authors: Gordon M. , Irvine P. , Kennedy J. W. 
Published: June 2010

AbstractRecent theoretical progress and major advances in computational methodology for spinodal and critical points make Pulse‐Induced Critical Scattering (PICS) a fast and reliable tool for examining statistical mechanical hypotheses, as expressed in the free energy of mixing function for solutions of linear polymers, and for measurement of the moments Mr = Σiwimir of the molecular weight distribution. Theoretical interpretation of measured phase diagrams has been hampered by 1) a lack of sufficiently reliable information on Mr(r = 1, 2, 3) of samples available from standard sources, and 2) the mental effort required in deriving spinodal and critical point equations from the increasingly complex free energy of mixing functions via the determinants of Willard Gibbs. Three strategies help to counter these difficulties: 1) Two molecular weight distributions (MWDs) are called r‐equivalent if they share at least the first r moments; computer software is available to determine the mixture of [r/2] sharp fractions which is r‐equivalent to a given MWD; thus the mixing of a small number of components gives access to an unlimited range of mixed samples whose moments are known (in terms of those of the components) to an accuracy set only by the analytical balance. 2) A spinodal truncation theorem (and critical point conjecture) exploits the concept of r‐equivalence since they determine the set of moments on which spinodal and critical point loci depend in addition to those moments featuring in the free energy expression. 3) Application of powerful algorithms of the QR‐type to the eigenvalue problems posed by the Gibbs spinodal and critical conditions have removed the necessity for prior excursions into the algebra of determinants by the human experimenter, since now spinodal and critical points can be numerically computed easily and directly from any postulated free energy function, especially when we employ the truncation theory and the notion of r‐equivalence. In consequence, the rapid feedback now possible with computer explorations of theoretical hypotheses is helpful in advancing the thermodynamics of polymer solutions and exploiting more fully the tools, such as PICS, for monitoring the relevant effects experimentally.
Gas‐ and liquid‐like phase dualism in polymers
Authors: Baranov V. G. , Frenkel S. 
Published: June 2010

AbstractAn analysis of the behavior of polymer systems in the condensed amorphous state shows that they may resemble both gases (e.g., high elasticity) and liquids (high density, ability to flow and crystallize, etc.). Moreover, polymer systems, analogously to gases, exhibit distribution according to their thermodynamic potentials, which for polymers is connected with the distribution according to end‐to‐end distances, while for gases it is related to the distribution according to velocities (in both cases we have a Maxwell distribution). The similarity between gases and macromolecules is also suggested by the low proper density of the latter (∼0.05 for the θ‐dimensions).The preceding facts allow us to formulate the concept of phase dualism, according to which each segment of the polymer system in the condensed state possesses at the same time features both gas‐like and liquid‐like. The occurrence of one or the other of the likenesses or their simultaneous occurrence depends on the direction and scale of the segment's reaction towards external effects (field of force, temperature, etc.). Keeping in mind the existence of phase dualism one may describe, at least in a thermodynamically formal way, virtually all the peculiar features of the behavior of polymer systems in various transitions.In particular, a quantitative and qualitative interpretation is possible of a nontrivial transition from crystallization with chain folding to crystallization with chain extension for when a system containing randomly coiled macromolecules is compressed on all sides. In this case the compression will affect the dual phase system in two ways. First, the segment liquid will be compressed while the internal energy will be reduced by ΔUt and second, the interaction between the segments will be strengthened. The thermodynamic characteristics of the “segment gas” under compression on all sides must be altered, losing some gas‐like qualities, towards the transition of the whole system into a “real liquid.” Such a transition is feasible if the statistical coil forms a compact globule, or if it becomes straightened and forms nematic structures, while the internal energy changes by ΔUg. An analysis of the thermodynamic losses caused by such transitions shows that a transition of the latter type, i.e., with unfolding of the macromolecular chains, is the more likely one. Earlier investigations carried out by us indicate that on reaching some critical degree of unfolding, a transition must occur from crystallization with folding to crystallization with extension, which, together with the conclusion mentioned above, explains the specificity of crystallization under hydrostatic compression. Quantitative evaluations of pressure at which the transition from one manner of crystallization to another should occur give P > 2500 atm, in good accord with the experimental data.
Spectrometer for the investigation of small‐angle neutron scattering using the time‐of‐flight method
Authors: Gladkikh I. , Kunchenko A. B. , Ostanevich Yu. M. , Cser L. 
Published: June 2010

AbstractInvestigation of small‐angle neutron scattering by the time‐of‐flight method and the basic characteristics of the spectrometer used are briefly described. First experiments with protein solutions confirming the suitability of the method are reported.
Polymer/polymer diffusion. I. Experimental technique
Authors: Price Fraser P. , Gilmore Paul T. , Thomas Edwin L. , Laurence R. L. 
Published: June 2010

AbstractDiffusional processes in polymer blends, although important in determining the characteristics of the blend, are poorly understood. Virtually no data are available in the open literature. A novel experimental technique useful in the study of diffusion in compatible polymer/polymer systems is presented. It uses a scanning electron microscope and dispersive energy analysis of the x‐ray fluorescence profile in the interdiffusion of two polymer components. The technique is used to determine the diffusivity in a poly(vinyl chloride)‐poly(±‐caprolactone) at 70°C. The diffusion coefficient [D = (1.59 ± .13) × 10−12cm2/sec] is of the same order as the only reported polymer/ polymer diffusion measurements.
Small‐angle X‐ray scattering from block polymer micelles
Authors: Legrand D. G. 
Published: June 2010

AbstractIt has been found that the AB block polymers of polystyrene and poly(dimethylsiloxane) form micelles in normal alkanes. The micelles are swollen by methylene chloride or cyclohexane which gives to an increased turbidity and an increased mobility of the polystyrene. Small–angle x–ray scattering data indicate that the polystyrene decreases in size as methylene chloride or cyclohexane are added. A model is proposed to explain these results.
Analysis of conformational contributions to polymer properties at the glass transition
Authors: O'Reilly James M. 
Published: June 2010

AbstractThe conformational contributions to the specific heat at constant volume by the chain backbone and side groups are reviewed. Calculations from rotational isomeric state models support the previous results for the backbone contribution for simple vinyl chains. Contributions from side chains are consistent with other experimental data. A rotational contribution in a liquid lattice is found in glass‐forming liquids. A conformational contribution to the relaxation of the adiabatic compressibility is discussed.