Miscibility in blends of random copolymers of styrene and acrylontrile with block copolymers of styrene and methyl methacrylate

Phase behavior in blends of random copolymers of styrene and acrylonitrile with block copolymers of styrene and methyl methacrylate was studied by light scattering, light microscopy and glass transition temperature measurements. The results are compared with those of respective blends containing random copolymers of styrene and methyl methacrylate. In terms of macrophase separation, the block copolymers display a more extended miscibility domain with styrene/acrylonitrile copolymers than the random copolymers. However, the extent of the miscibility domain varies as a function of temperature. Unlike the random copolymer blends, all blends containing block copolymers exhibit lower critical solution temperature behavior. Finally, it is established that the systems studied here undergo spinodal decomposition leading to macrophase separation.     

EPR Imaging Determination of High Molecular Weight Nitroxide Radicals in the UV Degradation of Polycarbonate‐Poly(acrylonitrile‐butadiene‐styrene) Polymers

The determination of nitroxide concentrations and distributions across plaques of polycarbonate/acrylonitrile‐butadiene‐styrene copolymer blend (PC/ABS) containing a high molecular weight hindered amine stabilizer (HALS) exposed to thermal and photochemical degradation treatments by EPR and EPR imaging (EPRI) is reported. Three different polymer compositions were examined: PC/ABS blends not‐pigmented and white pre‐pigmented with titanium dioxide; neat polycarbonate (PC); neat acrylonitrile‐butadiene‐styrene copolymer (ABS). The distribution profiles of the nitroxide radical in the various samples show large differences in the radical concentration across the plaques, these differences depending on the nature of the polymer and on the degradation treatment (thermal or photochemical). The experimental information provides important details on the mechanism of degradation of a complex polymeric matrix such as PC/ABS.

     

Nachweis von teilverträglichkeit in den phasengrenzflächen von polymergemischen mittels IR-spektroskopie

Among the various methods for determining compatibility in polymer blends infrared spectroscopy, especially the FT IR method, because of its sensitivity, is a rather simple tool to detect specific interactions as a necessary condition for compatibility in polymer blends. As a special advantage, in addition to hints for compatibility, from FT IR spectroscopy informations about the functional groups involved are obtained. By means of FT IR spectroscopy in blends of poly(oxymethylene) (POM) and polymers with ester groups like poly(methyl methacrylate) (PMMA) or poly(tetramethylene terephthalate) (PBTP) the existence of intermolecular interactions between carbonyl groups and the oxygen atoms of POM can be shown. This gives a possibility to detect very weak interactions which cannot be seen with the usual compatibility methods. Nevertheless, such weak interactions may enhance properties like processing behavior or toughness by an increased adhesion between the brittle matrix polymer and the dispersed elastomer phase in impact modified polymer systems.     

Polymere und Copolymere mit p-Vinyl-α.α-diphenyläthylen-Grundbausteinen

p-Vinyl-α.α-diphenylethylene (pNDPÄ) was polymerized radically in bulk at 80°C and copolymerized with styrene. The resulting polymers and copolymers had relatively low degrees of polymerization (ranging from 10 to 100). The polymerization took place primarily via the vinyl group and to a lower extend via the vinyliden group. The unsaturated side group enabled subsequent crosslinking reactions with these polymers. Copolymers with pVDPÄ-groups having higher molecular weights were obtained by GRIGNARD reaction of p-vinyl benzophenone/styrene copolymers with methyl magnesium iodide. These copolymers yielded the corresponding macromolecular polyanions upon treatment with naphthalene sodium in tetrahydrofuran; the latter were able to start graft-copolymerization of acrylonitrile, methylmethacrylate, and styrene; when using styrene, living side chains were formed. It was shown by dissolution experiments that no ungrafted backbone polymer and no free homopolymers were present in the graft-copolymers with acrylonitrile and methylmethacrylate.     

Zur polymerisation und copolymerisation von α-methoxystyrol

α-Methoxysyrene cannot be homopolymerised, neither by an anionic nor by a cationic or free radical mecanism. This monomer is more reactive in the cationic copolymerisation than vinyl ethyl ether. Its incapability to form longer sequences indicates a low ceiling temperature. In the free radical copolymerisation with styrene, acrylonitrile, methacrylate and methyl methacrylate (MMA) the parameter for α-methoxystyrene is always found to be zero. From the parameters of the first three comonomers the Q-and e-values are estimated to Q = 0.65 and e = -1.20. The relatively low Q-value and very low reactivity towards poly (MMA radicals) demonstrate the occurance of considerable steric hindrance during polymerisations with α-methoxystyrene.     

Fracture and structure of ABS polymers

ABS polymers are made from blends of styrene/acrylonitrile copolymer with polybutadiene rubber latices grafted with styrene/acrylonitrile copolymer. The rubber particles in the grafted latex are covered with hemispherical hillocks of styrene/acrylonitrile copolymer approximately 0.1 to 0.15 microns in size. When fractured at ?180°C. the rubber particles in ABS polymers are pulled out of the matrix and this allows their structure to be studied by electron microscopy. This behaviour of the rubber particles appears to be due to the rubber and matrix having different mechanical properties, despite the fact that both are well below their glass transition temperatures. The existence of a strong bond between the rubber and matrix is revealed by structure on the base of cavities from which rubber particles are torn. This structure is interpreted as being due to plastic deformation and fracture of the matrix at the interface between the two phases. Some fracture surfaces exhibit extensive plastic deformation of the matrix between rubber particles.     

Free Radical Co‐ and Terpolymerization Reactions of Methyl Methacrylate,Acrylonitrile, 4‐Vinylpyridine,and Styrene in Microemulsion

The oil‐in‐water microemulsion copolymerization reactions of styrene (S) and acrylonitrile (AN), AN and methyl methacrylate (MMA), S and 4‐vinylpyridine (4‐VP), respectively, and the microemulsion terpolymerization reactions of S, MMA and AN started by water soluble potassium peroxodisulfate (KPS) as radical initiator are investigated. The copolymerization diagrams and the reactivity ratio (r) values of the polymerization reactions in solution and in microemulsion are compared with each other. Rheological investigations have shown the polymers produced in microemulsion to exhibit special properties due to their high molecular weights. Glass transition temperatures, decomposition temperatures, and melt indices of the products obtained from the free radical polymerization in microemulsion and from polymerization in solution are compared with each other. Infrared and Raman spectra of the terpolymers (S/AN/MMA) produced in microemulsion are presented; typical vibrations are assigned.     

Analyse der phasenstruktur von binären polymersystemen

Two sets of polymer blends have been prepared by mixing solutions or melts of polystyrene with polybutene-1(poly(1-ethylethylene)), cellulose acetate, poly(methyl methacrylate), polyisobutylene, atactic polypropylene, poly(vinyl chloride), high pressure polyethylene, and of poly(vinyl chloride) with high pressure polyethylene, ABS, poly(vinylidene chloride), poly(vinyl acetate), vinyl chloride/vinyl acetate copolymer. The phase structure of these blends was analysed by microscopic and differential calorimetric measurements and by determination of the turbidity of the films. Phase diagrams were prepared from the glass transition temperatures and melting points taken from DSC curves. In this analysis all systems show a distinct phase separation ensuing from incompatibility. The only exception is the blend: poly(vinyl chloride) + vinyl chloride/vinyl acetate copolymer.     

Synthèse de polystyrènes chlorométhylés renfermant des radicaux tétrathiafulvalène carbonyloxyméthyles

In order to solve the problem of polymer swelling, which limits the resolution for negative resists, new resists were developed which show no swelling. The undesirable swelling can be suppressed by converting nonpolar crosslinked polymers into polar ones, which are soluble after irradiation. This aim was attained by mixing a polystyrene bearing tetrathiafulvalenyl (TTF) groups with 1,2-dibromo-1,1,2,2-tetrachloroethane. For our study, we applied resists including poly(4-chloromethylstyrene)s containing tetrathiafulvalenecarbonyloxymethyl groups ( 1 and 2 ). Poly(4-chloromethylstyrene)s ( 4 ) or poly[styrene-co-(4-chloromethyl)styrene]s ( 5 ) with a variety of controlled molecular weights and molecular weight distributions were prepared by radical chain polymerization. The reaction of cesium tetrathiafulvalenecarboxylate ( 3 ) with 4 or 5 was carried out and the resultant substituted polymers 1 and 2 were characterized.     

The Gordon-Taylor equation. Additivity and interaction in compatible polymer blends

An analysis of the Gordon-Taylor equation shows that its background is based on additivity. The corresponding parameter K = ρ₁ Δα₂ / (ρ₂ Δα₁), however, may include also an interaction contribution if the quadratic concentration term is neglected in a virial-like extension of the glass transition temperature vs. composition expression. Then K becomes a real fitting parameter. It is shown that a distinction of the two cases is possible by using the corresponding linearized form of the respective equations. The discussion of data of polystyrene/poly(2,6-dimethyl-1,4-phenylene oxide), styrene copolymers/poly(2,6-dimethyl-1,4-phenylene oxide) and poly(methyl vinyl ether)/polystyrene blends gives evidence for the decisive influence of the stiffer component on the glass transition behaviour of compatible polymer blends.     

Nanoscale Blends between Immiscible Polymers via Simultaneous Non‐Interfering Polymerisation

Summary: An important topic in polymer science seeks to improve the performances of polymer blends using nanoscale phase segregation. Here, blends between polystyrene and polycaprolactone are realised by a chemical route. The non‐interfering character of the radical polymerisation of styrene and the lanthanide halide initiated ring‐opening polymerisation of caprolactone is assessed. The molecular weights range from 2 000 to 3 500 for polycaprolactone and up to 140 000 for polystyrene, with reasonable polydispersity indexes. From calorimetry measurements, it is shown that polystyrene and low molecular weight polycaprolactone are immiscible. The morphology of the blends between the two immiscible polymers studied by atomic force microscopy is consistent with nanometer‐scale phase segregation.

AFM surface image of a nanoscale blend.     

Miscibility of phenoxy polymer/polyacrylate blends

The miscibility of blends of phenoxy polymer 1 from bisphenol A and epichlorohydrin and polyacrylates is studied using differential scanning calorimetry (DSC) and Fouriertransform infrared (FTIR) spectroscopy. The DSC curves show that poly(alkyl acrylate)s are immiscible with phenoxy. IR spectra show that there exists weak hydrogen-bonding interaction between poly(methyl acrylate) and phenoxy. The miscibility behavior of various phenoxy/polyacrylate blends cannot be satisfactorily explained by a non-hydrogenbonded solubility parameter approach. It can be better explained by the polar and nonpolar solubility parameter approach.     

Bestimmung der ungestörten Dimensionen von Makromolekülen aus Lichtstreuungsmessungen unter Berücksichtigung der Molekulargewichtsverteilung

Formulae are given for the polymolecularity correction factors of two variants of the Baumann procedure for the determination of the unperturbed dimensions of macromolecules, exhibiting a Schulz-Flory or a logarithmic normal distribution of molecular weights. The experimental check with poly(α-methylstyrene), [poly(1-methyl-1-phenylethylene)] mixtures, which to a good approximation have Schulz-Flory or logarithmic normal distributions of molecular weights, respectively, demonstrates that for the Baumann-Stockmayer-Fixman and the Baumann-Kurata-Stockmayer procedures the linear extrapolation is possible for polymer homologues with any width of the molecular weight distribution and that it results in the same values for the unperturbed dimensions as for polymer homologues with narrow molecular weight distribution, provided the values for the weight average molecular weight M_w and the z-average mean square radius of gyration 〈S?²〉_z are multiplied with the corresponding polymolecularity correction factors q_Mw, and q_Sz, respectively.     

Concentration Fluctuations and Segmental Dynamics in Weakly Dynamic Asymmetric Blends in the Presence of Surface‐Functionalized Multiwall Carbon Nanotubes

Surface‐functionalized multiwall carbon nanotubes (MWCNTs) are incorporated in poly(methyl methacrylate)/styrene acrylonitrile (PMMA/SAN) blends and the pretransitional regime is monitored in situ by melt rheology and dielectric spectroscopy. As the blends exhibit weak dynamic asymmetry, the obvious transitions in the melt rheology due to thermal concentration fluctuations are weak. This is further supported by the weak temperature dependence of the correlation length (ξ ≈ 10–12 Å) in the vicinity of demixing. Hence, various rheological techniques in both the temperature and frequency domains are adopted to evaluate the demixing temperature. The spinodal decomposition temperature is manifested in an increase in the miscibility gap in the presence of MWCNTs. Furthermore, MWCNTs lead to a significant slowdown of the segmental dynamics in the blends. Thermally induced phase separation in the PMMA/SAN blends lead to selective localization of MWCNTs in the PMMA phase. This further manifests itself in a significant increase in the melt conductivity.

     

Herstellung und antivirale Wirksamkeit von Polyacrylsäure und Polymethacrylsäure

The antiviral activity of a number of fractions of poly(acrylic acid)s and poly(methacrylic acid)s with different tacticities, different molecular weights and molecular weight distributions has been investigated. Isotactic poly(acrylic acid)s are essentially more antiviral active in the whole area of efficacy than the atactic ones. Independent of the tacticity poly(acrylic acid)s with molecular weights smaller than 5000 show no significant effects, polymers with molecular weights greater than 25000 are toxic in the used doses. The optimum of efficacy is between 6000 and 15000. Isotactic poly(acrylic acid)s with narrow molecular weight distributions are more active than those with broad distributions. The atactic poly(acrylic acid)s with lower efficacy do not show this relationship. Atactic poly(methacrylic acid)s are not antiviral active in vivo compared with untreated controls. Isotactic ones have a just detectable efficacy which is essentially lower than the activity of the atactic poly(acrylic acid)s.     

Synthesis of Hyperbranched Polymers by Anionic Self‐Condensing Vinyl Polymerization

Anionic self‐condensing vinyl polymerization is achieved from an in situ creation of a vinyl monomer bearing an active anion by the reaction of equimolar amount of 1,3‐diisopropenylbenzene (DIPB) and butyllithium in THF at 30°C. Onset of the intermolecular‐equilibrium between isopropenyl groups (α‐methylstyrene) and isopropenyl‐α‐methylstyryllithium sites of the oligomer restricts the growth of hyperbranched poly‐(DIPB) in THF at –40°C. Addition of a small amount of styrene interrupts this equilibrium. Conversion of isopropenyl‐α‐methylstyryllithium into styryllithium sites quickly directs the consumption of styrene and concurrent intermolecular‐condensation into remaining α‐methylstyrene groups of the oligomers. Thus, the equilibrium is reestablished and it has been shifted to the right by one or more α‐methylstyrene units that increase the molecular weight of the hyperbranched living polymer. Repeated small additions of styrene are attended by impressive multiplications of molecular weights. Up to seven generations of hyperbranched polymers have been synthesized as reported in this paper; the polymers exhibit high molecular weight and broad molecular weight distributions (1.8 < M̄_w/M̄_n < 4). The Mark‐Houwink exponent, α, is found to be 0.38 indicating a densely packed three‐dimensional structure resulting from the hyperbranched topology.     

Relative importance of side reactions in the RLi-acrylonitrile — dimethylformamide system

The probability of interaction of anionically growing poly(acrylonitrile) chains with dimethyl-formamide (DMF) in the acrylonitrile (AN)-RLi-DMF system was investigated by means of NMR data, poly(acrylonitrile) synthetized with various ROLi initiators does not contain traces of DMF fragments. Quantum chemical calculations were carried out taking CH₃? CH₂CH(CN)? Li as a model compound and simulating the anionic active site of AN. The results obtained show that the interaction of this compound with AN is highly preferred (by 100 kJ/mol) to that with DMF. Qualitatively similar results are related to the butyllithium(BuLi)-AN and BuLi-DMF systems. However, the reaction between BuLi and DMF is exothermic (in contrast to that between the active site of the model compound with DMF). This fact is in agreement with the effective addition of BuLi to DMF in the absence of any competing compound.     

Synthèse de polystyrènes chlorométhylés renfermant des radicaux tétrathiafulvalénylphénoxyméthyles

In order to study the influence of the nature of the moiety bearing a tetrathiafulvalenyl group in the polymers upon the microlithographic properties of resists, poly(p-chloromethylstyrene)s and poly(styrene-co-p-chloromethylstyrene)s containing the 4-tetrathiafulvalenylphenoxymethyl group with a variety of controlled molecular weights and molecular weight distributions were studied. The copolymers were all prepared by reaction of poly(4-vinylbenzyl chloride) with potassium 4-tetrathiafulvalenylphenolate ( 3 ). Without exception, the resulting poly[p-chloromethylstyrene-co-p-(tetrathiafulvalenylphenoxymethyl)styrene]s are highly insoluble. However, by reaction of potassium 4-tetrathiafulvalenylphenolate with poly(styrene-co-p-chloromethylstyrene) soluble copolymers could be prepared.     

Acetic Anhydride – Accelerating Agent for Nitroxide‐Controlled Free‐Radical Copolymerization of Styrene and Acrylonitrile

The influence of acetic anhydride on the controlled radical copolymerization of styrene and acrylonitrile was studied. If benzoyl peroxide/2,2,6,6‐tetramethylpiperidine‐N‐oxyl (BPO/TEMPO) are used the addition of acetic anhydride up to a molar ratio of additive/TEMPO = 2 : 1 results in a twelve times higher rate of polymerization. The molecular weights are increased and the molecular weight distributions are slightly broadened. A further increase of this molar ratio did not accelerate the polymerization rate further, but broadened the molecular weight distributions. Contrarily, the influence of acetic anhydride on the PS‐TEMPO controlled radical copolymerization is less pronounced. By means of UV‐VIS spectroscopy the reduction of the concentration of free TEMPO through reaction with acetic anhydride at 125°C in ethylbenzene was demonstrated.     

Molmassenabhängigkeit der Geschwindigkeitskonstanten der Adsorption von Polybutylmethacrylat aus Cyclohexan

The kinetics of adsoprtion of poly(butyl methacrylate) on iron powder from cyclohexane as solvent is determined by measuring the polymer concentration during adsorption for different molecular weights. There is an inverse relationship between the rate constant of adsorption k and the molecular weight of polymer. This corroborates theoretical results, which involve the quality of solvent: k ～ 1/M^2a where a is the Kuhn-Mark-Houwink exponent. Thus it is possible to determine the quality of solvent by investigations of adsorption using polymers of various molecular weight. Good coincidence with the a-value received from viscosity data via the Kuhn-Mark-Houwink relationship is achieved in the case of cyclohexane.