Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenylene oxide)/chlorinated polyethylene blends

The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.     

Thermotropic poly[oxy(2,6-dimethyl-1,4-phenylene)]-block-poly(oxyterephthaloyloxy-1,4-phenylenealkylene-1,4-phenylene)

Block copolymers containing a rigid [oxy(2,6-dimethyl-1,4-phenylene)] block and thermotropic poly[oxyterephthaloyloxy-1,4-phenylene-hexamethylene (or/and decamethylene)-1,4-phenylene] blocks were synthesized. Their structures were examined by means of ¹H and ¹³C NMR and X-ray diffraction, and their liquid crystalline properties investigated by polarizing microscopy.     

Effect of the catalyst-monomer ratio on the molar mass and glass transition temperature of poly(oxy-2,6-dimethoxy-1,4-phenylene)

2,6-Dimethoxyphenol was polymerized using Ag₂O-triethylamine complex as catalyst and a study made of the effect of the catalyst-monomer ratio on the yield, molar mass and polydispersity of poly(oxy-2,6-dimethoxy-1,4-phenylene). The glass transition temperatures T_g were measured with a computerized differential scanning calorimeter. The effect of the molar mass on T_g of poly(oxy-2,6-dimethoxy-1,4-phenylene) is discussed. The equation, T_g = T_{g, ∞} ? K/M, describes well the dependence of T_g on the viscosity-average molar mass M_v from 1900 to 176000 g/mol. Some poly(oxy-2,6-dimethyl-1,4-phenylene) samples were studied as reference material.     

Miscibility behavior in blends of poly(2,6-dimethylphenylene oxide) and random or block copolymers of styrene with methyl methacrylate

The Miscibility in blends of poly(2,6-dimethylphenylene oxide)

1 Systematic IUPAC name: poly[oxy(2,6-dimethyl-1,4-phenylene)].

(PPO) with random or block copolymers of styrene and methyl methacrylate (MMA) was studied by light microscopy and glass transition temperature measurements. Blends of PPO and the random copolymers were found to be miscible up to a copolymer content of 18 wt.-% MMA. The transition from miscibility to immiscibility in these blends in independent of temperature in the range 100 to 350°C. From these data, the segmental interaction parameter between units of the homopolymer and MMA, χ_PPO/PMMA is estimated to be about 0,5. Blends of PPO and the block copolymers of styrene and MMA used behave essentially as the corresponding homopolymers in terms of miscibility.     

Low temperature modification of polymers by triazolinediones. Electrophilic substitution of poly(oxy-2,6-dimethyl-1,4-phenylene)

Poly(oxy-2,6-dimethyl-1,4-phenylene) (PPE, 8 ) is reacted with substituted 1,2,4-triazoline-3,5-diones 1 to give the partially substituted poly[oxy-2,6-dimethyl-3-(1,2,4-triazoline-3,5-dione-1-yl)-1,4-phenylene] 9 . The reaction occurs via electrophilic substitution of the electron-rich PPE with the highly electron deficient triazolinediones 1 . For low degrees of substitution, the reaction readily occurs at room temperature. The inherent viscosity decreases with increasing substitution. The results are compared to similarly substituted polybutadiene. The glass transition temperature of the substituted PPE's decreases with the content of triazoline groups, a result which is interpreted by a distortion of the packing in glassy PPE.     

Synthesis and characterisation of poly(arylene sulfides), 6. Synthesis of block copoly(arylene sulfides)

Novel ABA block copolymers of poly(1,4-phenylene sulfide) (PPS(A)) and poly-(2-methyl-1,4-phenylene sulfide) (PMPS(B)) were synthesised from bis(4-bromophenyl) sulfone (BBS) by sequential reaction with copper(I) 4-bromo-2-methylbenzenethiolate (CBMT) and copper(I) 4-bromobenzenethiolate (CBT). PPS, PMPS and PPS/PMPS random copolymers were also prepared to aid block copolymer characterisation. Polymer fractions were studied by hot-stage microscopy to evaluate melting ranges, and molar masses were computed from bromine end-group concentrations and from gel permeation chromatography studies. Compositional analyses were made by IR and ¹H NMR spectroscopy leading to confirmation of the block copolymer structure and to evaluation of the degrees of polymerisation of the individual blocks.     

Zum Mechanismus der oxidativen Kupplung von Phenolen

In order to make a decision between the quinone acetal equilibration/quinone acetal rearrangement and the so far discussed SET mechanism for the oxidative coupling of 2,6-xylenol to poly(oxy-2,6-dimethyl-1,4-phenylene) the polymerization was carried out in the presence of 5-(2,6-dimethylphenoxy)-2-methoxy-1,3-xylene ( 1 ) (the methylated dimer) or α-methyl-ω-phenoxypoly(oxy-1,4-phenylene) [O-methylated poly(phenylene ether)] ( 2 ). GC and GPC studies indicated that neither 1 nor 2 are incorporated into the polymer. These observations exclude the SET-mechanism according to Scheme 4.     

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.     

Thermal expansion of poly(oxy-2,6-dimethoxy-1,4-phenylene)

The thermal expansion coefficient of poly(oxy-2,6-dimethoxy-1,4-phenylene), PPOO, was measured from 150 to 500 K, using a thermomechanical analyzer connected to a computer for the data handling. Poly(oxy-2,6-dimethyl-1,4-phenylene), PPO, and some brominated poly(oxy-2,6-disubstituted-1,4-phenylene)s were studied as reference materials. The apparent glass transition temperatures of the high molar mass polymers were 456 K for PPOO and 487 K for PPO, and the changes in cubic thermal expansion coefficients at T_g were 6,01 · 10^?4 K^?1 for PPOO and 4,23 · 10^?4 K^?1 for PPO. The activation of the β-relaxation was found for PPOO at 260 K and attributed to the hindered torsional oscillations of the backbone phenylene groups. Another transition was found at 160 ? 170 K and interpreted as the γ-relaxation due to the oscillatory motion of the methoxy groups. Reasons for the differences in the thermal expansion behaviour of PPOO and PPO are discussed.     

Effect of cooling rate on the structural relaxation of poly(oxy-2,6-dimethoxy-1,4-phenylene) and poly(oxy-2,6-dimethyl-1,4-phenylene)

The activation enthalpies for the structural relaxation of poly(oxy-2,6-dimethoxy-1,4-phenylene) and poly(oxy-2,6-dimethyl-1,4-phenylene) were determined by studying the dependence of the limiting fictive temperature on the cooling rate, using a differential scanning calorimeter (DSC) interfaced to a computer. The molar mass dependence of the activation enthalpies complied with the empirical equation, ΔH^˙ = ΔH ? A/M, where ΔH is the activation enthalpy of an infinite chain length polymer, M_v is the viscosity-average molar mass, a = 0,64, and A is a constant that depends on the free volume of the chain ends of the polymers. The values of ΔH are 433 kJ/mol for poly(oxy-2,6-dimethoxy-1,4-phenylene) and 449 kJ/mol for poly(oxy-2,6-dimethyl-1,4-phenylene).     

Synthesis of amorphous poly(thioarylene)s via oxidative polymerization of diaryl disulfides

Amorphous poly(thioarylene)s containing a methyl substituent and/or an ether bond in the main chain were prepared via oxidative polymerization of diaryl disulfides using 2,3-dichloro-5,6-dicyanobenzoquinone. The resulting poly(thio-2,6-dimethyl-1,4-phenyleneoxy-1,4-phenylene) having alternating ether and thioether bonds shows a better solvent solubility and has a higher glass transition temperature (T_g) (182°C) than non-substituted poly(thio-1,4-phenylene). Polymerization of methyl substituted diphenyl ether derivatives with disulfur dichloride has been also developed for a one-pot synthesis of amorphous poly(thioarylene)s.     

Micelle formation and polyisobutylene solubilization by polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene block copolymers

Thermodynamics of micellization and the structure of micelles formed by polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene block copolymers were studied. A molar mass influence on the aggregation number of micelles was found. The lower the molar mass, the higher the micelle aggregation number. The solubilization of polyisobutylene by micelles of these copolymers in methyl isobutyl ketone was also examined. The saturation concentrations of polyisobutylene solubilized by different block copolymers in methyl isobutyl ketone were determined by laser light scattering. The solubility curves found were linear and dependent on the molar mass of the polyisobutylene solubilized and the copolymer. The logarithm of the maximum amount of polyisobutylene solubilized by mass unity of the triblock copolymer varies linearly with the logarithm of the molar mass of the polyisobutylene. This variation is hardly dependent on the copolymer molar mass and strongly dependent on the type of block copolymer.     

Block copolymers with poly(oxy-1,4-phenylene) and liquidcrystalline polyester segments

Block copolymers were synthesized composed of an isotropic, crystallizable poly(oxy-1,4-phenylene) block and a thermotropic liquid-crystalline (LC) polyester block. Crystalline as well as amorphous LC polyesters were used, derived from substituted poly(1,4-phenylene terephthalate). The block of poly(oxy-1,4-phenylene) was introduced via telechelic 1 . 1 was prepared with a functionality of 2 in a Cu-catalyzed reaction of 4-bromophenolate 4 with 4,4′-isopropylidenediphenol (bisphenol A). The molecular weight of the telechelic is given by the ratio 4 /bisphenol A. The increase in molecular weight during formation of the block copolymer is shown by viscosity and gel-permeation chromatography measurements. The maximum weight loss of the block copolymer as obtained by thermogravimetry is in the range of 450–500°C. Both segments in the block copolymers have a strong influence on their mutual crystallization behaviour. Short segments of poly(oxy-1,4-phenylene) suppress the crystallization of both blocks. When using longer segments of poly(oxy-1,4-phenylene) the melting endotherms of both blocks are observed, but the degree of crystallinity is lower than that of the homopolymers. The fracture behaviour of the liquid-crystalline polyester 2a is changed by modification with 20 wt.-% of poly(oxy-1,4-phenylene) and the shear-banded texture is lost.     

Bioinspired All‐Polyester Diblock Copolymers Made from Poly(pentadecalactone) and Poly(2‐(2‐hydroxyethoxy)benzoate): Synthesis and Polymer Film Properties

The bioinspired diblock copolymers poly(pentadecalactone)‐block‐poly(2‐(2‐hydroxyethoxy)benzoate) (PPDL‐block‐P2HEB) are synthesized from pentadecalactone and dihydro‐5H‐1,4‐benzodioxepin‐5‐one (2,3‐DHB). No transesterification between the blocks is observed. In a sequential approach, PPDL obtained by ring‐opening polymerization (ROP) is used to initiate 2,3‐DHB. Here, the molar mass M_n of the P2HEB block is limited. In a modular approach, end‐functionalized PPDL and P2HEB are obtained separately by ROP with functional initiators, and connected by 1,3‐dipolar Huisgen reaction (“click‐chemistry”). Block copolymer compositions from 85:15 mass percent to 28:72 mass percent (PPDL:P2HEB) are synthesized, with M_n of from about 30 000–50 000 g mol^?1. The structure of the block copolymer is confirmed by proton NMR, Fourier‐transform infrared spectroscopy, and gel permeation chromatography. Morphological studies by atomic force microscopy (AFM) further confirms the block copolymer structure, while quantitative nanomechanical AFM measurements reveal that the Derjaguin–Muller–Toporov moduli of the block copolymers range between 17.2 ± 1.8 and 62.3 ± 5.7 MPa, i.e., between the values of the parent P2HEB and PPDL homopolymers (7.6 ± 1.4 and 801 ± 42 MPa, respectively). Differential scanning calorimetry shows that the thermal properties of the homopolymers are retained by each of the copolymer blocks (melting temperature 90 °C, glass transition temperature 36 °C).     

Heat capacity of poly(oxy-2,6-dimethoxy-1,4-phenylene)

The heat capacities of poly(oxy-2,6-dimethoxy-1,4-phenylene) were measured from 160 to 480 K using a differential scanning calorimeter (DSC) interfaced to a computer for data collection and processing. The values for the heat capacities between 160 and 420 K were tabulated. Below 280 K they depend only slightly on the molar mass, whereas above 280 K the conformational changes of the end groups have a noticeable effect. Wunderlich's addition scheme for the calculation of heat capacities from the empirical group contributions gives results that agree within ± 1% with the experimental data. The heat capacity jump ΔC_p at T_g depends inversely on the molar mass. Wunderlich's “bead” model for ΔC_p values is discussed for poly(oxy-2,6-disubstituted-1,4-phenylene).     

Thermotropic liquid-crystalline aromatic polyester-graft-poly(2,6-dimethyl-1,4-phenylene oxide) copolymers

Dicarboxy-terminated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) macromonomers were prepared and subjected to the preparation of tailor-made aromatic thermotropic liquid-crystalline (LC) polyester-graft-PPO copolymers. The macromonomers were obtained by hydrolysis of dimethyl carboxylate-terminated PPO macromonomers without cleavage of the PPO chains, which were derived from PPO oligomers with a terminal phenolic OH-group and a bromo derivative of isophthalate. The tailor-made aromatic thermotropic LC graft copolymers were prepared by direct polycondensation from the dicarboxy-terminated macromonomers, p-hydroxybenzoic acid, aromatic dicarboxylic acids and diphenols at definite mole ratios in pyridine in the presence of diphenyl chlorophosphate as a condensation reagent. The polyester-graft-PPO copolymers are thermally stable up to 280–300°C and show a thermotropic LC nematic phase in spite of introduction of PPO grafts on the polyester backbones.     

Rubber modification of poly(2,6-dimethyl-1,4-phenylene oxide)/crosslinked polystyrene semi-interpenetrating polymer networks: morphology and impact behaviour

Rubber modification of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/crosslinked polystyrene (CPS) semi-interpenetrating polymer networks (semi-IPNs) was studied using polybutadiene (PB), a linear styrene-butadiene-styrene (SBS) triblock cocpolymer and a star-shaped SBS multi-block copolymer, at different composition ratios. The materials, obtained by reactive compression moulding of mixtures containing PPO, an elastomer, styrenic monomers and crosslinker (divinylbenzene), show a very high glass transition temperature (T_g), high dimensional stability and good impact properties.     

Telechelic poly(thio-1,4-phenylene)s and poly(thio-1,4-phenylene)-block-polyamides

Poly(thio-1,4-phenylene)s (PPS) 5a–d with reactive end groups like carboxyl, nitro, cyano and aldehyde groups were synthesized under high as well as atmospheric pressure. Carboxyl terminated telechelics 5a were used as starting materials for the synthesis of poly(thio-1,4-phenylene)-block-polyamides. Semicrystalline and amorphous polyamides like Nylon 6 and Trogamide® served as coblocks. The formation of block copolymers was approved by the solubility behavior, the NMR and IR spectra as well as high temperature GPC. The thermal stability increases with the fraction of PPS. By DSC, phase separation of the block copolymers was observed at certain compositions and molecular weights.     

Poly(2,6-Dimethyl-1,4-Phenylene oxide)/crosslinked polystyrene semi-interpenetrating networks: Synthesis and properties

Semi-interpenetrating networks (semi-IPN's) based on linear poly(phenylene ether)s and crosslinked polystyrene can be prepared by reactive moulding of crosslinkable polymeric mixtures. These materials show thermomechanical properties which strongly depend on both the ratio of the two polymeric matrices and the degree of crosslinking in the polystyrene network. Samples based on a 50/50 weight ratio of poly(2,6-dimethyl-1,4-phenylene oxide)/crosslinked polystyrene show glass transition temperatures (T_g) which are very dependent on the degree of crosslinking. It is therefore possible to obtain materials with desired T_g, ranging from the T_g of the corresponding linear blend to that of poly(2,6-dimethyl-1,4-phenylene oxide) alone.     

Evaluation of kinetic parameters resulting from photostabilized degradation of poly(2,6-dimethyl-1,4-phenylene oxide) films in the absence and presence of zinc bis(O,O′-diisopropyldithiophosphate)

Light scattering was used to evaluate the resulting changes in molecular weight, root-mean-square radius of gyration, degree of polymerization, number of chain scissions per single chain kngth, degree of degradation, specific rate constant, energy of activation, enthalpy, entropy and free energy of activation for the photo-oxidative degradation of poly(2,6-dimethyl-1,4-phenylene oxide) (poly(oxy-2,6-dimethyl-1,4-phenylene)) film, both in the presence and absence of 0,1 wt.-% zinc bis(O,O'-diisopropyldithiophosphate) (ZnDTP) as photostabilizer, undergoing random chain scission and crosslinking processes in the temperature range 313–363 K with light of wavelength 365 nm. The inhibitive action of ZnDTP was discussed from the viewpoint of the amount of gel fraction.