Thermoplastic elastomers by sequential monomer addition

The living carbocationic polymerization (LC Pzn) of p-methylstyrene (pMeSt) was achieved by the use of the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl₄ initiating system in the presence of triethylamine (Et₃N) electron donor in CH₃Cl/nC₆H₁₄ mixed solvent at-80°C. Next, the synthesis, characterization, and some physical-mechanical characteristics of a series of poly (p-methylstyrene-b-isobutylene-b-p-methylstyrene) (PpMeSt-PIB-PpMeSt) triblocks is described. The latter synthesis involved two steps in one reactor: 1) The generation of diliving polyisobutylene dications (PIB) by the dicumyl chloride (DiCumCl)/TiCl₄ system under similar conditions followed by 2) The addition of pMeSt and growth of living PpMeSt cations. The PpMeSt-PIB-PpMeSt triblocks are soft thermoplastic elastomers (TPEs).Paper L in the series Living Carbocationic Polymerization     

New polyisobutylene based model ionomers

Three-arm star polyisobutylene ionomers (¯M_n=8800) with terminal SO₃ M (M=K or Ca²) groups were synthesized and their mechanical properties investigated. Compression molded films displayed high elongations, i.e., -1000% for Ca² ionomers with lower values for the K counterions. Strain induced crystallinity was observed at higher elongations. Mechanical properties in general compared favorably with conventional covalently linked rubbery networks and were comparable and in some cases superior to EPDM-based ionomers carrying randomly distributed SO₃ M groups.For the first two parts see Proceedings, 28th IUPAC Macromolecular Symposium, Amherst, MA, July 11–16, 1982, p. 905 and 906     

Phase transition in swollen gels

Summary The swelling and mechanical behaviour of networks of copolymers of acrylamide, methylenebisacrylamide and sodium 2-(2-carboxybenzoyloxy)ethylmethacrylate (mole fraction of salt x _s =0–0.2) in water-acetone mixtures was investigated. In the range x _s 0.01 phase transition (collapse) was observed, with both the extent of the collapse and the critical acetone concentration in the mixture at collapse, a _c , increasing with increasing concentration of the salt. A comparison between these results and those obtained for networks with a quaternary ammonium salt led to a conclusion that an exchange of the positive charge of the ammonium salt (NCl) for the negative charge of the sodium salt (COONa) in the side chain decreases the critical content of salt necessary for the collapse, X _s ^c , from 0.03 to 0.01, and the collapse takes place at lower concentrations of acetone. The collapse may also take place in a mixed solvent waterethanol; the dependence of network swelling on the concentration of ethanol is roughly the same as that on the concentration of acetone.     

Multi-arm star polyisobutylenes

Summary The first synthesis of a multi-arm radial-star polyisobutylene (*-PIB) is described. The synthesis occurred by the addition of excess divinylbenzene (DVB) linking reagent to a living polyisobutylene (PIB) charge i.e., by the arm first method under specific conditions. The radial structure of the *-PIB was proven by determining the molecular weight of a sample by light scattering, then selectively destroying the aromatic polydivinylbenzene (PDVB) core, and finally determining the molecular weight of the surviving alphatic PIB arms. The synthesis strategy, kinetic observations during synthesis, and procedures leading to a representative *-PIB are described. This product whose g/mole with , contained 90.3 mole% (78 wt.%) PIB arms and 9.7 mole% (22 wt.%) aromatic core; thus the number of PIB arms emanating from the core was (number average number of arms)=56 or (weight average number of arms)=110.     

Phenomenological model of the scale effect of the strength of polymer fibers

A new derivation of the scale effect equation for polymer fibers is proposed. The equation is: AL ^–, where is the average strength of the fiber; L is the length of the fiber; A and are coefficients. The equation was obtained from the general premises of scale effect theory without indication of the concrete form of the probability function F(S).Ukrainian Scientific-Research Institute of Polymer Fibers, Kiev. Translated from Khimicheskie Volokna, No. 4, pp. 34–36, July–August, 1992.     

Critical solution point and chain dimension of branched-polystyrene solutions

Summary Critical solution point and chain dimension were measured for branched polystyrene(BPS) in solution as a function of molecular weight(M) and compared with those for linear polystyrene(LPS). The critical concentration _c of BPS was quite different from that of LPS at a fixed M, but the same at a fixed overlap-concentration ^*, i.e., plots of _c vs. ^* fall on a single straight line for both BPS and LPS (gf_c ^*). Reduced critical temperature _c defined by gt_c=(–T_c)/ [T_c: critical temperature, : the -temperature] was related to _c as _{c c} ² for BPS, whereas _{c c} for LPS.     

Rate of radical polymerization of N,N-dimethylaminoethyl methacrylate in cyclohexane

Summary Anions of propene, isobutylene and cycloheptatriene have been prepared using Lochmann's Base. Star polymers in the form of one arm star, two arm star and three arm star polymers of styrene have been synthesized from the allyl anion (2), 2-methylenepropylenyl dianion (4) and the cycloheptatrienyl trianion (6) respectively, with acid end groups by quenching the living polymers with carbon dioxide. The number average molecular weight has been determined by stoichiometry, HPSEC and end group analysis by titration.     

Variable‐temperature IR spectroscopic studies of CO adsorbed on Na‐ZSM‐5 and Na‐Y zeolites

CO interacts with extraframework alkali metal cations (M⁺=) of zeolites to form both M⁺CO and M⁺OC species. By using variabletemperature FTIR spectroscopy, these Cbonded and Obonded species were found to be in a temperaturedependent equilibrium. For the same cation, the difference in interaction energy depends upon the zeolite framework. Thus, for the equilibrium process ZNa⁺=CO ZNa⁺OC, where Z represents the zeolite framework, H ⁰ was found to take the values 3.8 and 2.4 kJ mol^– for CO/NaZSM5 and CO/NaY, respectively. The Cbonded species show always the highest cation–CO interaction energy.     

New polymer syntheses

Summary Various poly(ether sulfide)s were prepared by polycon-densation of 4-mercaptophenol or silylated 4-mercaptophenol with 2,6-dichloropyridine or 3,6-dichloropyridazine. A two step and an one-pot procedure were compared. The poly-(ether-sulfide)s were characterized by elemental analyses, inherent viscosities, ¹³C-NMR spectroscopy, gel-permeation chromatography and DSC-measurements.     

Antifungal polyoxygenated fatty acids fromAeollanthus parvifolius

Two polyoxygenated fatty acids with antifungal activity have been isolated from aerial parts ofAeollanthus parvifolius (Labiatae) using bioassay-guided isolation procedures. Spectroscopic analysis was used to identify the compounds as (Z)-4,9-diacetoxy-6,7-epoxy-5-hydroxy-8-oxododeca-2-enoic acid and (Z)-4,6,7,9-tetraacetoxy-5-hydroxy-8-oxododeca-2-enoic acid. Both of these compounds inhibited spore germination ofCladosporium cucumerinum. Minimum inhibitory doses were 1 µg and 5 µg, respectively, but only the former inhibited germination ofAspergillus niger at a dose of 5 µg. Neither compound exhibited antibacterial activity. (Z)-4,9-Diacetoxy-6,7-epoxy-5-hydroxy-8-oxododeca-2-enoic acid reduced the hyphal growth ofPythium ultimum. The mode of action was not resolved but did not involve either the disruption of the cell wall membrane or the inhibition of extracellular enzymes. Application of (Z)-4,6,7,9-tetraacetoxy-5-hydroxy-8-oxododeca-2-enoic acid to seedling plants did not give any protection against fungal attack, and indeed the compound appeared to be phytotoxic.     

Copolymerization of 2-phenoxy-1,3,2-dioxaphosphorinanes with α-keto acids involving deoxygenation of the keto oxygen atom: deoxy-copolymerization

Summary The copolymerization of 2-phenoxy-1,3,2-dioxaphosphorinanes (4) with -keto acids (2) took place at room temperature without added catalyst to produce copolymers (5). The copolymer 5 is composed of phosphoric acid triester unit (5 ) and of -hydroxy-carboxylic acid ester unit (5 ). Unit 5 is an alternating unit of monomers 4 and 2 whereas unit 5 is formed by deoxygenating 2 by 4. 5 can be taken as copolymers of units 5 and 5 , the formation of the latter involving a deoxygenation process (Deoxy-Copolymerization). The ratio of 5 /5 (m-value in 5) increased in the order of unsubstituted (4a)-, 5,5-dimethyl (4b)-, and 5-t-butyl (4c)-phosphorinane systems. The reaction mechanism is also discussed.Dedicated to the 65th birthday of Professor G. Manecke     

Synthesis and characterization of poly(1-sila-cis-pent-3-enes) substituted with pendant pyridinyl groups

Poly[1-methyl-1-[3-(3-pyridinyl)propyl]-1-sila-cis-pent-3-ene], poly[1-phenyl-1-[3-(3-pyridinyl)propyl)-1-sila-cis-pent-3-ene], and poly[1-phenyl-1-(4-pyridinyl)-1-sila-cis-pent-3-ene] were synthesized by the anionic ring-opening polymerization of 1-methyl-1-[3-(3-pyridinyl)propyl]-1-silacyclopent-3-ene, 1-phenyl-1-[3-(3-pyridinyl)propyl]-1-silacyclopent-3-ene, and 1-phenyl-1-(4-pyridinyl)-1-silacyclopent-3-ene, respectively. These are the first polycarbosilanes which contain heterocyclic pyridine units as side-chain substituents. These polymers were characterized by¹H,¹³C, and²⁹Si NMR as well as by IR and UV spectroscopy. The molecular weight distributions were determined by gel permeation chromatography, glass transition temperatures, by differential seanning calorimetry: (DSC) and thermal behavior, by thermogravimetric analysis. (TGA).     

A study of the acidic and catalytic properties of pure and sulfated zirconia–titania and zirconia–silica mixed oxides

Protonated pyridine (PyH⁺) was not found on ZrO₂ (Z) or ZrO₂–TiO₂ (ZT), but was detected on sulfated oxides (ZS, ZTS) by IR spectroscopy. In contrast, ZrO₂–SiO₂ samples containing about 30–80 mol% ZrO₂ showed Brønsted acidity both in nonsulfated (ZS) and sulfated (ZSS) forms. The total acidity was determined by NH₃TPD. Introduction of sulfate ions increased the sitespecific catalytic activity (TOF) in the conversion of cyclopropane or nhexane. The effect of sulfate ions was more significant on samples rich in zirconia. Results suggest that Zr is homogeneously distributed in ZS samples rich in silica. Zirconiabound dimeric sulfate, generating strong acidity, could not be formed in these preparations due to the absence of fairly large ZrO₂ domains.     

Specific features of the phase transformations occurring during the sintering process of the beta-alumina based ceramics and their properties

Conclusions During the sintering process of beta-alumina obtained using the method of plasmochemical synthesis, the structural transformation occurs and it is accompanied by the separation of the excess Na₂O and the formation of an intergranular meltlike phase that is saturated with sodium and is characterized by high dielectric properties.The quantity of the meltlike phase and the magnitude of the /( + ) ratio determine the degree of stabilization (stability) and the final resistivity of the material and depend on the initial chemical composition and the heating rate maintained during the sintering process.It was shown that when the duration of residence of the material in the hot zone of the furnace is increased or when the specimens sintered maintaining high heating rates are subjected to additional heat treatment, one observes the occurrance of the reverse structural transformation that is characterized by an increase of the phase ratio /( + ) 1, a reduction in the quantity of the meltlike phase right up to its complete disappearance, and a decrease of the electrical resistivity of the material.In the materials having a large excess quantity of sodium oxide, the process of crystallization of the intergranular NaAlO₂ phase occurs simultaneously with the second phase transformation.The best ceramic and electrophysical parameters were obtained when sintering the material contained 7.9% Na₂O.Translated from Ogneupory, No. 3, pp. 13–18, March, 1990.     

Redox 1∶1 alternating copolymerization of cyclic acyl phosphonte with 4,4′-diphenoquinones

Summary A cyclic phosphonite(1) was copolymerized with 4, 4-diphenoquinones (2a–2c) to give 11 alternating copolymers (3a–3c) consisting of a carboxylic acid ester and a triaryl phosphonate ester. Copolymerization took place without added initiator. During the reaction 1 was oxidized whereas 2 was reduced (redox copolymerization). A mechanism involving a genetic zwitterion intermediate (4) is proposed for the copolymerization.     

Livig carbocationic polymerization

Summary Diblock copolymers of isobytylene (IB) — methyl vinyl ether (MeVE) have been prepared by sequential monomer addition by employing 2-chloro-2, 4, 4-trimethylpentane (TMPCl)/TiCl₄ initiating system in the presence of nBu₄NCl or dimethyl-acetamide (DMA) in CH₂Cl₂/hexanes at –80°C. In line with our earlier observations (1), living carbocationic polymerizations (LCPZn) were obtained in the presence of nBu₄NCl (i.e., the molecular weight of the poly(vinyl methyl ether) segment increased upon TiCl₄ addition), however, extensive chain transfer occurred in the presence of DMA. According to column chromatography analysis, the product prepared in the presence of nBu₄NCl is essentially pure PIB-b-PMeVE diblock (96w%) contaminated with a very small amount (4w%) of PIB. In contrast, the product obtained with DMA contains only 21w% PIB-b-PMeVe together with 72w% PIB and 5w% PMeVe homopolymers. This large difference in blocking efficiencies suggests that the structures of the growing species are different in the presence of the common anion salt,nBu₄NCl, and the electron donor, DMA.For paper LIII in this series see Polym. Bull., vol. 29/1     

Studies concerning charged nickel hydroxide electrodes IV. Reversible potentials in LiOH,NaOH, RbOH and CsOH

The variation of reversible potential E_r with log a_moh and has been studied for several nickel hydroxide/oxyhydroxide couples in various alkali hydroxides. Both activated and deactivated -phase couples show only a small dependence ofE _r with log_moh (or where known) in LiOH, NaOH, RbOH and CsOH electrolytes. The change in MOH content on oxidation/reduction is found to be about 0.1 mol MOH per two-electron transfer and is the same as found previously in KOH. These results confirm that the bulk oxidized -phase lattice is devoid of alkali cation although a small quantity may be adsorbed by the surface. On the other hand both activated and deactivated /-phase couples show a marked dependence of 0.45 mol MOH per two-electron transfer in LiOH, NaOH and RbOH (at concentrations > 0.5 m), also in good agreement with earlier data for KOH. On the basis of these results a general stoichiometry can be inferred for the -phase, namely M_0.32NiO₂ · 0.7H₂O where M=Li⁺, Na⁺, K⁺ or Rb⁺. Measurements imply that the Cs⁺ ion or the Rb⁺ ion at low concentration (<0.5 m) do not enter the interlayer structure of the -phase. This behaviour is thought to be related to the low Rb-O and Cs-O bond strengths afforded by the -phase structure.     

Studies on electrical conductivity of gamma irradiated polyaniline

Summary de electrical conductivity at surface of -irradiated polyaniline (PAn) has been studied. EPR spectroscopic results indicate that the variation of spin concentration is consistent with the increase of _de. Electrical conductivity (_de) versus temperature (T) characteristics of unirradiated and irradiated PAn were performed, which demonstrate that the unirradiated curve can fit to ln_deT₁, while the irradiated curve fit to ln_deT_1/4.     

Syntheses and Properties of Aromatic Polyimides Based on 1,1-Bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane and 1,1-Bis[4-(4-aminophenoxy)phenyl]-1-phenylethane

A series of fluorinated polyimides were prepared from 1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane with various aromatic tetracarboxylic dianhydrides via a conventional two-step procedure. These polyimides were amorphous in nature and afforded flexible and tough films. Some polyimides derived from less stiff dianhydrides were soluble in polar organic solvents. The glass-transition temperatures (T _g) of these polyimides ranged from 252 to 324C, and softening temperatures (T _s) stayed in the 254322C range. Decomposition temperatures (T _d) at 10% weight loss all occurred above 569C in both air and nitrogen atmospheres. For a comparative study, another series of analogous polyimides based on 1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenylethane were also pepared and characterized.     

A parametric study of copper deposition in a fluidized bed electrode

The behaviour of a fluidized bed electrode of copper particles in an electrolyte of deoxygenated 5×10^–1 mol dm^–3Na₂SO₄–10^–3mol dm^–3H₂SO₄ containing low levels of Cu(II), is described as a function of applied potential, bed depth, flow rate, particle size range, Cu(II) concentration and temperature. The observed (cross sectional) current densities were more than two orders of magnitude greater than in the absence of the bed, and current efficiencies for copper deposition were typically 99%.No wholly mass transport limited currents were obtained, due to the range of overpotentials within the bed. The dependence of the cell current on the experimental variables (excluding temperature) was determined by regression analysis. The values of exponents for some of the variables are close to those expected, while others (for concentration and flow rate) reveal interactions between the experimental parameters. Nevertheless the values of the correlation coefficient matrix are low (except for the term relating expansion and flow rate), so that cross terms may be neglected in modelling the system at the first level of approximation.Nomenclature d mean particle diameter (mm) - E electrode potential, ( _m– _s)_r+(x) (V vs ref) wherer denotes the value of ( _m- _s) at the reversible potential - I (membrane) current density (A m^–2) - L static bed depth (mm) - M concentration of electroactive species (mol dm^–3) - T catholyte temperature (K) - u catholyte flow rate (mm s^–1) - x distance in the bed from the feeder electrode atx=0 - XL expanded bed depth (mm) - bed expansion (fraction of static bed depth) - _m metal phase potential (V) - _s solution phase potential (V) - _m metal phase resistivity (ohm m) - _s solution phase effective resistivity (ohm m) - overpotential (V)