Lamellar structure in melt crystallized low density polyethylene

Summary The mechanochemically initiated copolymerization (by vibratory milling) of acrylonitrile (AN) with vinyl acetate (VA) and with alpha-methyl styrene (MS), at room temperature, was studied. The reactivity ratio values: AN — VA r_AN=2.850 r_VA=0.159 AN — MS r_AN=2.550 r_MS=0.272 calculated according to an analytic procedure, as well as by the Kelen-Tüdös method, are quite different from those already given in literature, indicating the existence of a different copolymerization mechanism.     

Terpolymerization: A Review

The terpolymer, poly (styrene-acrylonitrile-linalool) has been synthesized by free radical solution polymerization of the electron-donating monomers, linalool (optically active) (LIN) and styrene (STY) with the electron-accepting monomer, acrylonitrile (AN) using benzoyl peroxide (BPO) as an initiator and xylene as diluent at 75°C for 40 minutes. The system follows ideal kinetics. Rp [BPO]^0.5 [LIN]^1.0 [STY]^1.0 [AN]^1.0. ¹H-NMR spectrum of terpolymer has peaks at 7.8–8.0 due to –OH group of LIN and at 7.0–7.7 due to phenyl group of styrene. ¹³C-NMR spectrum of terpolymer has peaks at ppm = 119–120 of –CN, ppm = 129–136 of C₆H₅ and ppm = 75–77 of –C–OH. Bands at 3075 cm^–1, 2240 cm^–1 and at 3500 cm^–1 are observed in the FTIR spectrum of terpolymer, indicates the presence of phenyl, cyanide and hydroxy group respectively. The reactivity ratios, determined by the Kelen–Tüdös method [r ₁ for AN and r ₂ for (LIN + STY)] are 0.11 and 0.005 respectively. It is concluded that the system agrees with theoretical treatment and gives the relative reactivity ratio k ₁₂/k ₁₃=0.748 by treatment of the free radical propagating mechanism. The overall activation energy is 38 kJ/mol. The molecular weight of terpolymer is determined by gel permeation chromatography technique. The value of _w/ > _n is 1.36.     

Phase separation temperatures in the polystyrene—poly(α-methyl styrene)—methylcyclohexane system

The phase separation temperatures (PST) in the ternary system polystyrene (PS) (M_w = 1.75 × 10⁴ g mol⁻¹ — poly(α-methyl styrene) (PαMS) (M_w = 6.0 × 10⁴) — methylcyclohexane (MCH) and the binary systems PS-MCH and PαMS-MCH have been determined by using a He---Ne laser light-scattering apparatus over the total polymer weight fraction (W_{PS + PαMS}) range of 0.018 to 0.80 and various polymer blend ratios. The PST determined at a scattering angle of 0° agreed with those at 90° for the binary systems over polymer concentrations of 0.1 to 0.7 and for the ternary over W_{PS + PαMS} of higher than 0.3. Deviations of the PST determined at an angle of 90° from those at 0° were observed in the ternary system when W_{PS + PαMS} was lower than 0.3. Two phase separation temperatures, at which the intensity scattered from zero angle changed discontinuously, are observed at concentrations lower than W_{PS + PαMS} = 0.042 in the ternary system. The PST in the ternary system decreases monotonically with increasing W_{PS + PαMS} over 0.3 to 0.7. The phase diagram for the PS-PαMS-MCH system at W_{PS + PαMS} = 0.8 is characterized by a maximum PST around − 14°C.     

Polymerization of an Acetoxyvinyl Substituted Chlorocyclophosphazene

The vinyl acetate derivative, gem-isopropyl-2-(-acetoxyvinyl)tetrachlorocyclotriphosphazene (1), has been used in radical homopolymerization and copolymerization reactions with methyl methacrylate, (MMA) and styrene. The 1,1-disubstituted olefin did not undergo radical homopolymerization. Copolymers derived from MMA and 1 contained only low amounts (<2 mol%) of 1. A maximum incorporation of 20 mol% of phosphazene monomer was achieved with styrene as comonomer. The data obtained in low- and high-conversion copolymerizations with styrene were used to calculate the monomer reactivity ratios. The results of the calculations show that the terminal model is not operative. Calculation for the penultimate model with r ₂=0 resulted in r ₁ and r₁ values of 2.8±0.2 and 0.7±0.1, respectively. For the hypothetical homopolymer of 1 a T _g value of 441 K was calculated. All the copolymers with styrene exhibit flame-retardant properties.     

Radical copolymerization behaviors of styrene and coumarin

The radical copolymerizations of styrene (M₁) with coumarin (M₂) (and 7-acetoxycoumarin) have been first carried out in benzene (and in DMF) at 60° C using AIBN as initiator. The terminal model monomer reactivity ratios (MRR) were determined by Fineman-Ross method, Kelen-Tudos method and nonlinear method. The respective estimated values are r₁ = 43.08, r₂ = 0.63; r₁ = 39.17, r₂ = 0.43; and r₁ = 49.94, r₂ = 1.04 for styrene-coumarin (S-C) system. For styrene-7-acetoxycoumarin (S-AC) system, the values are r₁ = 51.44, r₂ = 1.24; r₁ = 50.56, r₂ = 1.20 and r₁ = 56.23, r₂ = 1.48, respectively. The penultimate model MRRs are determined by Fenn-Barson method and nonlinear method to be r₁= 49.18, r₁ = 2.01, r₂ = r₂ = 0.43 and r₁ = 51.21, r₁ = 0.86, r₂= r₂ =0, respectively, for S-C system; r₁ = 64.76, r₁= 3.46, r₂ = r₂= 1.20 and r₁ = 59.90, r₁ = 0.57, r₂ = r₂ = 0. respectively, for S-AC system. It is found that coumarin is about 1.2 times more reactive toward styrene-terminated radical than 7-acetoxycoumarin for steric reasons. The penultimate model of Fenn-Barson is fairly adequate in describing the copolymerization mechanism of styrene-coumarin system, while the terminal model is more suitable for styrene-7-acetoxycoumarin system.     

Synthesis of novel random and block copolymers of tert-butyldimethylsilyl methacrylate and methyl methacrylate by RAFT polymerization

Hydrophobic-hydrolysable copolymers consisting of methyl methacrylate (MMA) and tert-butyldimethylsilyl methacrylate (TBDMSMA) have been synthesized for the first time by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization technique using cumyl dithiobenzoate (CDB) and cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents (CTAs). The monomer reactivity ratios for TBDMSMA (r₁ = 1.40 ± 0.03) and MMA (r₂ = 1.08 ± 0.03) have been determined using a non-linear least-squares fitting method. Well-defined random copolymers PMMA-co-PTBDMSMA have been prepared. Then, the versatility of the RAFT process to synthesize silylated block copolymers with controlled molecular weights and low polydispersities has been demonstrated using two strategies: the synthesis of PMMA-SC(S)Ph or PTBDMSMA-SC(S)Ph as macro-chain transfer agent (macro-CTA) for use in a two step method or an one-pot method which consists in the successive addition of the two monomers. Diblock copolymers with narrow molecular weight distributions (PDI < 1.2) were obtained from the one-pot method with number-average molecular weight values within the range 10,000-22,000 g mol⁻¹.     

Neue photoreaktive Polymere mit seitenständigen Dimethylmaleinimid-Gruppen. I. Radikalische homo-und copolymerisation von N-(5-methyl-3-oxa-4-oxo-hexen-5-yl)-dimethylmaleinimid

The homopolymerisation of N-(5-methyl-3-oxo-4-oxo-hexen-5-yl)-dimethylmaleimide (DMI-MA) leads to linear poly(methylmethyacrylates) with pendant lightsensitive dimethylmaleimide groups. Due to steric hindrance of the methyl substitutents, the carbon-double bond is not involved in the reaction, even at conversions of over 90%. The reaction velocity constant for the homopolymerisation is k_p/k = 2,0 – 2,2.10^?2 (65°C, toluene, AIBN) and the activation energy E_a = 62,36 ± 2 KJ/mol^?1. Measurement of the copolymerisation reactivity ratios for the monomer pairs DMI-MA/methacrylic acid (MAS), DMI-MA/methylmethacrylate (MMA) and DMI-MA/ethylacrylate (EA) gave the following values: DMI-MA (r₁): MAS (r₂) = 1,36 ±0,06 : 0,77: ± 0,06; DMI-MA (r₁) : MMA (r₂) = 1,16 ± 0,17:0,475 ± 0,17 and DMI-MA (r₁): EA(r₂) = 1,60 ± 0,15: 0,44 ± 0,15.     

Radical copolymerization of (−)-menthyl 2-acetamidoacrylate and styrene or methyl methacrylate near ceiling temperature

Radical copolymerization of chiral monomer, (−)-menthyl 2-acetamidoacrylate (1), with low ceiling temperature (T_c = 62.0 °C in [monomer] = 1.0 mol/L) and styrene or methyl methacrylate (MMA) has been studied near ceiling temperature (60 °C) and at the temperature lower than T_c (30 °C). Monomer reactivity ratios and Alfrey-Price Q and e-values of 1 are estimated to be r₁ = 0.27, r₂ = 0.067, Q = 3.0, and e = 1.2 at 30 °C, and r₁ = 0.32 and r₂ = 0.046 at 60 °C for the copolymerization of 1 (M₁) and styrene (M₂), suggesting an alternating tendency at both temperatures, whereas for the copolymerization of 1 (M₁) and MMA (M₂) r₁ and r₂ are estimated to be 2.9 and 0.019 at 30 °C, respectively, indicating longer sequence length of 1. Specific rotation and circular dichroism of the resulting copolymer indicate that styrene, in particular, is effectively incorporated into a helical copolymer structure at 60 °C and even only 25 mol% incorporation of the acetamidoacrylate unit in the copolymer induces the helix formation in solution.     

Characteristics of Heterophase Radical Graft Polymerization of Methyl Methacrylate on Polymer Fibres

Graft copolymers with graft PMMA were synthesized using the Cu²⁺—H₂O₂ redox system. The conditions for obtaining graft PCA—PMMA and HC-PMMA of 40–60 composite composition with grafting efficiency at the 85% level are found. The effect of the polymer matrix on the kinetic and thermodynamic properties of graft polymerization of MMA is revealed. Possible schemes of the reactions of graft polymerization of MMA to polycaproamide and hydrated cellulose are proposed based on quantum chemical calculations of the enthalpy of formation of the graft copolymers.The research was conducted under MNTPP Project No. 203 Chemical Engineering (Section 2 General Chemical Engineering) in the scientific-industrial program Higher-Education Research on Priority Directions in Science and Engineering.__________Translated from Khimicheskie Volokna, No. 1) pp. 19–23, January–February, 2005.     

Plasma-induced polymerization

Summary High molecular weight methyl methacrylate (M₁) — styrene (M₂) copolymers were obtained by plasma-induced bulk copolymerization. The reactivity ratios, determined by Kelen — Tüdös method, were shown to be r₁=0.41±0.01 r₂=0.57±0.01 and the coisotactic alternating addition probability G=0.48±0.02. These data indicate a radical mechanism of copolymerization.Dedicated to Professor Herman Mark at the occasion of his 85th anniversary     

The Effect of the Synthetic Conditions on the Deposition and Distribution of Copper Complexes on Polymer Supports

The influence of conditions (e.g., ratios of components, temperature etc.) on the reaction of Cu(OCOCH₃)₂·2H₂O with polyethylene grafted-polyacrylic on the amount of the metal and the composition of the immobilized Cu(II) complexes was studied. The concentration dependence obeys the Langmuir law. Analysis of the data leads to an evaluation of the stability constant for the Cu(II) complexes (K=300 l/mole at 333 K). The constant corresponds to a Cu(II) fixation value, k=0.35 mole/l (22.22 mg Cu(II)/g). The multistage fixation mechanism for Cu(II) complex formation was demonstrated by the marked atom technique. Cu(II) is fixed by one carboxylate group (to 16 mol% of the supported Cu(II), K ₁=16×10^–2 mole/g) and by two carboxylate groups (K ₂=2.54×10^–3 mole/g) of the grafted ligands. The PE-gr-PAA–Cu(II) system mimics the situation-insoluble support-soluble functional polymer covering and realizes the advantages of both the soluble and the three-dimensional crosslinked polymer. Steady-state magnetic susceptibility measurements and ESR spectroscopy were used to study the distribution of cupric ion attached to a polyethylene-grafted poly(acrylic acid) support. The existence of three types of cupric ion complexes was demonstrated: (1) isolated complexes, (2) complexes bonded by dipole–dipole interactions, and (3) clusters with strong exchange interactions. The mean distances between the isolated ions (¯r22–15 Å) and between the dipole–bound complexes (¯r _agreg7 Å) were estimated. The results obtained were compared to the data for other immobilized catalysts. Preliminary results on the fixation of bimetallic Cu(II) and Pd(II) complexes to the polymers as well as on their distributions were obtained.     

Preferential oxidation of CO in excess hydrogen over a nanostructured CuO–CeO2 catalyst with high surface areas

CuO–CeO₂ is prepared by coprecipitation and ethanol washing and characterized using BET, HR-TEM, XRD and TPR techniques. The results show that CuO–CeO₂ is nanosized (r_TEM = 6.5 nm) and possesses high surface area (S_BET = 138 m² g⁻¹). Furthermore, some lattice defects in the surface of CuO–CeO₂ are found, which are beneficial to enhance catalytic performance of CuO–CeO₂ in preferential oxidation of CO in excess hydrogen (PROX). Consequently, the nanostructured CuO–CeO₂ exhibits perfect catalytic performance in PROX. Namely, CO content can be lowered to less than 100 ppm at 150 °C with 100% selectivity of O₂ in the presence of 8% CO₂ and 20% H₂O at .     

Plasma-induced polymerization

Summary High molecular weight methacrylonitrile (M₁) — styrene (M₂) copolymers were obtained by plasma-induced bulk copolymerization. The reactivity ratios, determined by Kelen — Tüdös method, were shown to be r₁=0.21 and r₂=0.34 and indicate a radical mechanism of polymerization. Some microstructural aspects of the obtained copolymers are presented.     

A Novel Two-Dimensional Network Constructed by Bridged Salicylate and Pyrazine Ligands with Copper(II)

The coordination polymer, [Cu₂(sal)₂(pyz)(H₂O)₂] _n (H₂sal=salicylic acid, pyz=pyrazine), was synthesized and structurally characterized by X-ray crystallography. The empirical formula of the polymer is CuC₉NO₄H₈and the structural parameters are as follows: M _r=257.71, monoclinic, P2₁/c, Z=4, a=10.175(3) Å, b=7.352(4) Å, c=12.757(1) Å, =105.206(2)°, V=920.9(6) ų, D _c=1.859 g/cm³, (MoK)=23.62 cm^–1, F(000)=520 and the final R=0.048 for 2179 observable reflections. Each salicylate ligand connects the three copper centers to afford a novel 2-dimensional (2-D) network structure. The Cu^II-sal framework forms a rhombus type coordination framework. The pyz ligands fill the voids of the sheet and coordinate to the Cu site.     

p-acetyl benzylidene triphenylarsonium ylide initiated radical terpolymerization of styrene,acrylonitrile and copper acrylate: synthesis,characterization and properties

Solution terpolymerization of styrene (Sty), acrylonitrile (AN) and copper acrylate (CuA) has been carried out in dimethylformamide at 90°C for 4 h using p-acetyl benzylidene triphenylarsonium ylide as radical initiator. ¹H nuclear magnetic resonance (NMR), IR and elemental analysis have been used to characterized the terpolymer. Analysis of kinetic data indicates the following rate equation: The overall activation energy is 38 kJ mol⁻¹. The composition of terpolymer calculated from NMR and elemental analysis has been used to evaluate reactivity ratios as r₁(Sty) = 5 ± 2 and r₂(AN + CuA) = 0.4 ± 0.02 employing the Finemann–Ross method, which confirms its random origin. The terpolymer was thermally stable up to 2007deg;C.     

The Fluorescent Quantum Efficiency of Copolymers Containing Coumarin-6 at the Side-chain

Coumarin-6 containing acrylates (CA) with different spacers were synthesized. Copolymers of CA with methyl methacrylate (MMA) in CA/MMA in the weight ratios of 1/20, 1/40 and 1/60 were prepared by using AIBN as initiator. The copolymer compositions were determined from uv-visible spectroscopic analyses, according to Beer’s law. UV absorption and photoluminescence (PL) spectra indicated a concentration quenching, which increased with increasing coumarin-6 concentration in the copolymer compositions and also increasing the spacer length from the copolymer to coumarin-6 moiety, leading to a decreased fluorescence efficiency (φ_s/φ_o) as well as a red shift of λ_max. Furthermore, as the spacer, n in –(CH₂)_n–, increases from n=2, 3 to 6, excimers formed due to overlap of chromophores, resulting in the splitting of the PL emission band and lowering the PL intensity. Experimental results revealed that when the ratio of CA/MMA=1/60 and the spacer n=2, the copolymer film showed an optimized fluorescent quantum efficiency.     

Producing a fibre-forming copolymer of acrylonitrile with vinylene carbonate in homogeneous conditions

Conclusions 1. We have studied the copolymerization of AN with VC in homogeneous conditions. We calculated the copolymerization constants to be r_AN=14.9±0.1; r_VC=0.085±0.001.2. We selected conditions for producing fibre-forming copolymer, and obtained fibre with satisfactory mechanical indices.All-Union Scientific-Research Institute for Synthetic Fibres (VNIIV). Translated from Khimicheskie Volokna, No. 4, pp. 50–51, July–August, 1969.     

Novel Hyperbranched predominantly Alternating Copolymers Made From A Charge Transfer Complex monomer pair of p-(chloromethyl)styrene and Acrylonitrile via Controlled Living Radical Copolymerization

Summary Novel hyperbranched copolymers were successfully synthesized by the controlled charge transfer complex inimer and living radical copolymerization of p-(chloromethyl)styrene (PCMS) and acrylonitrile (AN). The resulting copolymers were characterized by SEC, NMR, FTIR, DSC and elemental analysis etc.. The influences of reaction conditions, such as the polymerization temperature, the catalyst (CuBr) concentration and the monomer ratio, on the resulting copolymers were investigated in detail. The monomer reactivity ratios were evaluated to be r_PCMS=0.937 and r_AN=0.088 respectively by the Fineman-Ross method. The higher are the polymerization temperature and the ratio of catalyst to monomer, the higher is the branching degree of the resulting copolymer. When the amount of monomer AN was used in excess than that of the monomer PCMS in the raw feed, the hyperbranched predominantly alternating copolymers HP[PCMS-co-AN] could be obtained. These hyperbranched copolymers were successfully used as functional macroinitiators to synthesize the star-shaped poly(PCMS-co-AN)/poly(MMA) block copolymers.     

Effect of the monomer ratio and initiating system on the disperse composition of polyacrylonitrile copolymers

Conclusions The mean size and polydispersity of polymer particles are increased on increasing the MMA/(AN, NaVS) ratio, as a function of the initiating systems used, in the following order: ammonium persulfate—rongalite, persulfate—bisulfite, and persulfate—metabisulfite.The PAN copolymer suspensions obtained under laboratory and under pilot plant conditions have identical mean particle sizes, but have a different disperse composition of the polymer particles.There is a slight dependence of the filterability resistance of polymer suspensions on the MMA/(AN, NaVS) ratio and on the initiating system used, which exerts no effect on the technological centrifuging regime.Of the investigated redox initiating systems, the most appropriae one for the manufacture of a PAN copolymer with an elevated MMA content is the ammonium persulfate—sodium bisulfite system.Bulgaria. Translated from Khimicheskie Volokna, No. 4, pp. 45–47, July–August, 1985.