Polymerization of coordinated monomers. V. Polymerization of methyl methacrylate–Lewis acid complexes

The polymerization of the complex of methyl methacrylate with stannic chloride, aluminum trichloride, or boron trifluoride was carried out in toluene solution at several temperatures in the range of 60° to ?78°C by initiation of α,α′-azobisisobutyronicrile or by irradiation with ultraviolet rays. The tacticities of the resulting polymers were determined by NMR spectroscopy. Both the 1:1 and the 2:1 methyl methacrylate–SnCl₄ complexes gave polymers with similar tacticities at the polymerization temperatures above ?60°C. With decreasing temperature below ?60°C, the isotacticity was more favored for the 2:1 complex, whereas the tacticities did not change for the 1:1 complex. On the ESR spectroscopy of the polymerization solution under the irradiation of ultraviolet rays at ?120°C, the 1:1 SnCl₄ complex gave a quintet, while the 2:1 SnCl₄ complex gave both a quintet and a sextet. The sextet became weaker with increasing temperature and disappeared at ?60°C. This behavior of the sextet corresponds to the change of the tacticities of polymer for the 2:1 SnCl₄ complex. An intra–intercomplex addition was suggested for the polymerization of the 2:1 complex, which took a cis-configuration on the basis of its infrared spectra. The sextet can be ascribed to the radical formed by the intracomplex addition reaction, while the quintet can correspond to that formed by the intercomplex addition reaction. The proportion of the intracomplex reaction was estimated to be about 0.25 at ?75°C, and the calculated value of the probability of isotactic diad addition of the intracomplex reaction was found to be almost unity.     

Molecular weight distribution and stereoregularity of polypropylenes produced with VCl4–AlEt2Cl catalyst

Dependences of the molecular weight distribution and stereochemical regulation of the polypropylenes produced with VCl₄–AlEt₂Cl catalyst on the polymerization temperature were examined. The molecular weight distributions of the polymers obtained at temperatures below ?40°C were unimodal and narrow (M _w/M _n ≤ 2). The molecular weight distributions obtained at higher temperatures (above ?21°C) were bimodal with one narrow distribution and one wide one (M _w/M _n > 2), and the polymer fraction of the wide distribution increased with the polymerization temperature. The fractional amount of ? (CH₂)₂? groups in the polymers, which corresponds to tail-to-tail linkage of two propylene units, increased to a maximum at ?21°C followed by a gradual decrease with the polymerization temperature. The production of isotactic polymers was confirmed at temperatures above ?21°C. From these data, it is concluded that only the homogeneous form of the catalyst system is responsible for the polymerization at temperatures below about ?21°C while the heterogeneous form appears and catalyzes the polymerization together with the homogeneous one at temperatures above ?21°C.     

Dynamic mechanical relaxation effects in some poly(arylene sulfones)

Poly-4,4′-oxydiphenylenesulfonyl and poly-4,4′-methylenediphenylenesulfonyl were synthesized by an electrophilic substitution polymerization of the arylene monosulfonyl chloride monomers. The glass-transition temperatures T_g of these polymers were determined by calorimetric and dynamic mechanical measurements, and the number-average molecular weights were determined by vapor-pressure osmometry. Both polymers were found to have the same T_g at equivalent molecular weight; the limiting value at high molecular weight is 238°C. Both polymers have two dynamic mechanical relaxation peaks at temperatures far below T_g. One is in the neighborhood of 0°C, and the other is at ?110°C. Plausible origins for these relaxations, and the absence of any near 0°C in poly(4,4′-isopropylidenediphenylene-co-4,4′-sulfonyldiphenylene dioxide), are discussed.     

Association of polyacrylonitrile prepared by low-temperature,solution polymerization with an organometallic catalyst

The weight-average molecular weights of polymers of acrylonitrile prepared by a free-radical initiator and an organometallic catalyst have been determined by lightscattering measurements in N,N-dimethylformamide, dimethyl sulfoxide, and dimethylacetamide at 25°C. and in dimethyl sulfoxide at 140°C. The apparent molecular weights of the polymers prepared with the NaAlEt₃S(i-Pr) catalyst in DMF at ?78°C. (referred to as high-melting polymers) changed from 54,800, 82,700, and 480,000 when measured in DMF at 25°C. to 36,000, 41,600, and 225,000 when measured in DMSO at 140°C., whereas the molecular weights of the free-radical polymers remained unchanged. Furthermore, from results obtained in DMSO at 140°C., The intrinsic viscosity–molecular-weight relationships were found to be identical for the high-melting and the free-radical polymer and in substantial agreement with an equation reported by Cleland and Stockmayer. The apparent decrease in molecular weight of the high-melting polymer from 25 to 140°C. indicates rather clearly that the high-melting polymers are associated in DMF at 25°C. The “aggregates,” even though present only at low concentrations, raised the weight-average molecular weight markedly but affected the number-average molecular weight only slightly, thus giving a high M?_w/M?_n ratio. It appears likely that when temperature and solvent are such that association does not occur, linear PAN's will have approximately the same intrinsic viscosity–molecular weight relationship (subject of course to slight change by polydispersity). The often reported abnormal molecular weight of samples prepared by solution polymerization especially at low temperatures, may be attributed to branching, or to an association, as reported here. The nature of association of PAN in dilute solution is also discussed.     

Dielectric study of relaxations and polymorphism in poly(diethyl siloxane)

The dielectric behavior of poly(diethyl siloxane) supports the adiabatic calorimetric findings of Beatty and Karasz. In particular, a sub-T_g transition is observed near ?180°C at 100 Hz, the glass transition near ?135°C at 100 Hz, and a first-order transition near ?70°C (crystal–crystal transformation). This glass-transition temperature is the lowest reported polymeric glass transition for polymers.     

Stereospecific polymerization of benzyl α-(alkoxymethyl) acrylates

α-(Alkoxymethyl) acrylates, such as methyl α-(phenoxymethyl) acrylate, benzyl α-(methoxymethyl)acrylate (BMMA), benzyl α-(benzyloxymethyl)acrylate, and benzyl α-(tert-butoxymethyl)acrylate, were synthesized, and their polymerizability and the stereoregularity of the polymers obtained by radical and anionic methods were investigated. The radically obtained polymers were found to be atactic by ¹³C- and ¹H-NMR analyses, but the polymers obtained with lithium reagents in toluene at −78°C were highly isotactic. Further, it is noteworthy that isotactic polymers were also produced with lithium reagents even in tetrahydrofuran. Effects of polymerization temperature and counter cation on stereoregularity were clearly observed in the polymerization of BMMA, and a potassium reagent afforded an almost atactic polymer. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 721–726, 1997     

Cyclo- and cyclized diene polymers. XIII. γ-Ray-initiated polymerization of 1,3-dienes

The γ-ray-initiated polymerization of butadiene, isoprene, and 2,3-dimethylbutadiene-1,3 was carried out at temperatures of 20°C. and ?78°C. Polymers of butadiene and isoprene with mixed linear and cyclic structure were proved to result from the polymerization at ?78°C. A monocyclic structure was found for the 2,3-dimethylbutadiene-1,3 polymers initiated either at ?78°C. or in the thiourea canal complex at 20°C.     

Synthesis and Characterization of Novel Organosoluble Polychloro Substituted Aromatic Poly(Ether Ketone)s

A novel monomer of tetrachloroterephthaloyl chloride (TCTPC) was prepared by the chlorination of terephthaloyl chloride catalyzed by ferric chloride at 175‐180 °C for 10 h, and confirmed by FTIR, MS and elemental analysis. A series of new polychloro substituted poly(aryl ether ketone)s with inherent viscosities of 0.58‐0.65 dL/g have been prepared from TCTPC with aromatic ether monomers by electrophilic Friedel‐Crafts acylation in the presence of DMF with anhydrous AlCl₃ as a catalyst in 1,2‐dichloroethane. Glass‐transition temperatures of these polychlorinated polymers ranged from 267 to 280 °C by DSC. The degradation temperature at 5% weight loss by TGA in nitrogen for these polymers ranged from 486 to 534 °C, and the char yields at 700 °C were 54‐65%. The polymers having a weight‐average molecular weight in the range of 65,900‐79,300 are all amorphous and readily soluble in polar solvents such as DMF, DMSO and NMP at room temperature. All the polymers formed transparent, strong, and flexible films, with tensile strengths of 86.1‐99.7 MPa, Young's moduli of 2.32‐3.35 GPa, and elongations at break of 10‐15%.     

γ-Ray-induced polymerization of α-haloacrylic acids

The γ-ray induced polymerizations of α-chloroacrylic acid, mp 66°C, and α-bromo-acrylic acid, mp 72°C, were investigated in the temperature range from 35°C to 85°C. An analysis of polymerization kinetics was made, and results were similar to those reported in the literature for other vinyl monomers. On heating of the polymer obtained, elimination of hydrogen halide takes place, and intramolecular lactone formation is observed. The rate of lactone formation of poly(α-chloroacrylic acid) obtained in the solid-state polymerization was found to be higher than that in the liquid state, because a highly isotactic configuration of polymers, tends to be formed in the solid-state polymerization, and elimination of hydrogen chloride is facilitated with an isotactic 5₂ helix structure.     

Dynamic mechanical properties of aromatic,aliphatic, and partially fluorinated epoxy resins

The α, β, and γ transitions at temperatures between ?200 and +100°C. of crosslinked aromatic and aliphatic epoxy polymers were determined from damping and shear modulus data, and compared with their fluorine containing analogs. Loci of segmental relaxation are suggested at various temperatures, and similarities between aliphatic and fluorocarbon segments, and polyethylene and polytetrafluoroethylene are discussed. Two systems of structurally similar monomers 2,2,3,3,4,4-hexafluoropentane diglycidyl ether-1,5 and 1,4-butane diglycidyl ether, and 2,2-bis(4-glycidyl phenyl ether)hexafluoropropane and 2,2-bis(4-glycidyl phenyl ether) propane were polymerized with the aid of two diamine curing agents, namely, ethylenediamine and m-xylylenediamine. Polymers of the aromatic diepoxides showed transitions with peaks at ?56°C. and above +70°C. Three main peaks were registered for the aliphatic and fluorocarbon diepoxides: at ?125 and at ?100°C., at ?56°C., and at 0°C. It is suggested that the T_g is affected by an interdependence of relaxation of all components of the polymer main chain.     

Dynamic mechanical relaxations of polyterephthalates based on trimethylene glycols

The dynamic mechanical relaxations of poly(trimethylene glycol terephthalate) (PTMT), poly(ditrimethylene glycol terephthalate) (PDTMT) and two copolymers obtained from them have been studied between ? 150 and 200°C with a dynamic viscoelastometer. The four polymers show three relaxations that are designated α, β, and γ in order of decreasing temperature. The α relaxation is considered to be the glass transition of the polymers. The β relaxation is wider and weaker than the α, as normally occurs in the polyester series. The γ relaxation takes place at temperatures below ? 100°C and is usually overlapped by the β relaxation. The influence of thermal and mechanical histories on the nature, location, and intensity of the three relaxations is studied and discussed.     

The dependence of slow crack growth in a linear polyethylene on test temperature and morphology

The slow crack growth behavior of a linear polyethylene with different morphologies was studied by using three point bending with a single edge notched specimen at testing tem-peratures from 30 to 80°C. The morphology was varied by annealing the quenched material at temperatures from 86°C to 135°C. It was found that at test temperatures of 60°C or less, the changes in failure time with annealing temperature are very similar to the change in density with a maximum at 130°C. At testing temperatures above 60°C, the relationship of between failure time and annealing temperature is altered when the test is in the range of the α transition temperature. These results indicate that with respect to slow crack growth in the case of a homopolymer the strength of the crystals is relatively more important than the number of tie molecules. © 1993 John Wiley & Sons, Inc.     

Synthesis and Characterization of Novel Organosoluble Methyl Substituted Poly(aryl Ether Ketone)s Containing Sulfone Linkage

Several new methyl substituted poly(aryl ether ketone)s containing sulfone linkage with inherent viscosities of 0.62–0.84 dL/g have been prepared from 4,4′‐bis(2‐methylphenoxy)diphenylsulfone and 4,4′‐bis(3‐methylphenoxy)diphenylsulfone with terephthaloyl chloride and isophthaloyl chloride by electrophilic Friedel‐Crafts acylation in the presence of DMF with anhydrous AlCl₃ as a catalyst in 1,2‐dichloroethane, respectively. These polymers having weight‐average molecular weight in the range of 71,000–49,000 are all amorphous and show high glass transition temperatures ranging from 167 °C to 191 °C, excellent thermal stability at temperatures over 400 °C in air or nitrogen, high char yields of 51–58% in nitrogen and good solubility in CHCl₃ and polar solvents such as DMF, DMSO and NMP at room temperature.     

The linear rheological responses of wedge‐type polymers

The linear rheological responses of a series of specially designed wedge‐type polymers synthesized by the polymerization of large molecular weight monomers have been measured. These wedge polymers contained large side groups which contained three flexible branch chains per polymer chain unit. The master curves for these polymers were obtained by time temperature superposition of dynamic data at different temperatures from the terminal flow regime to well below the glass transition temperature, T_g. While these polymers maintained a behavior similar to that of linear polymers, the influence of the large side group structure lead to low entanglement densities and extremely low rubbery plateau modulus values, being near to 13 kPa. The viscosity molecular weight dependence was also somewhat higher than that normally observed for linear polymers, tending toward a power law near to 4.2 rather than the typical 3.4 found in entangled linear chains. The glassy modulus of these branched polymers is also found to be extremely low, being less than 100 MPa at T_g ?60 °C. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 899–906     

Dendritic analogues of engineering plastics - a general one-step synthesis of dendritic polyaryl ethers

The first general single-step route to dendritic or cascade polyaryl ethers analogous to common linear polyaryl ethers is described. The sodium salts of four AB₂ monomers each containing a single phenolic hydroxyl group and two aryl fluorides activated toward nucleophilic substitution by carbonyl, sulphonyl, or tetrafluorophenyl moieties are shown to polymerize in hot N, N-dimethylacetamide. The products are high molecular weight polymers (7000 < M_n < 36000), have narrow polydispersities (1.50 < M_w/M_n < 4.50), and are highly soluble in organic solvents. The molecular weights of two of the polymers increase with monomer concentration. The polymers are thermally stable (500 °C under N₂) and have glass transition temperatures ranging from 135 to 231 °C.     

Polymerization of coordinated monomers. II. Stereoregulation in the free-radical polymerization of methacrylonitrile–zinc chloride or methacrylonitrile–stannic chloride complexes

The effect of complex formation on stereoregulation in free-radical polymerization was studied. Complexes of methacrylonitrile with ZnCl₂ and SnCl₄ were prepared and their properties and structures examined. The complexes were polymerized by initiation of α,α′-azobisisobutyronitrile or by irradiation with γ-rays from a⁶⁰Co source or ultraviolet rays either in solution or in bulk at various temperatures ranging from ?78 to 100°C. The triad tacticities of the resulting polymethacrylonitrile were determined by converting it to poly(methyl methacrylate) for NMR spectroscopy. The radicals in complexed forms were studied by ESR spectroscopy with the polymerization system in toluene irradiated with ultraviolet rays at ?120°C. The tacticities of the resulting polymers and their dependencies on the polymerization temperature were found to be characteristic of the complex species, i.e., the kind of metal chloride and the stoichiometry, being different from the tacticities and the dependencies, respectively, of the polymer obtained with pure methacrylonitrile. The 2:1 and the 1:1 complexes with SnCl₄ were found to give an eleven-line and a nine-line spectrum, respectively. On the basis of the results of both the tacticities and the ESR spectra, it was estimated that the proportion of the intracomplex reaction was 40%, and that the probabilities of isotactic diad addition of intra- and intercomplex reaction were 0.70 and 0.48, respectively.     

Positronium annihilation in amine-cured epoxy polymers

Positronium annihilation spectroscopy (PAS) has been used to study the microstructural properties of amine-cured epoxy polymers. We have determined the free-volume “hole” sizes in these polymers by comparing the observed ortho-positronium lifetimes with the known lifetime–free volume correlation for low-molecular-weight systems. The free volumes for four epoxies with different crosslink densities are found to vary significantly over the temperature range between ?78° and 250°C. The free-volume holes for these polymers are found to range from 0.025 to 0.220 nm³. Two important transition temperatures were found: one corresponds to the glass transition temperature T_g determined by differential scanning calorimetry (DSC), and the other occurs about 80–130°C below T_g. The sub-T_g transition temperature is interpreted tentatively as being where hole size reaches dimensions adequate for positronium trapping or else the onset temperature for local mode or side-chain motions. These two transition temperatures plus two additional onset temperatures are found to be correlated with crosslink densities calculated from stoichiometry.     

The rearrangement of benzylic trichloromethane-sulfenates to sulfoxides and chlorides

While benzyl trichloromethanesulfenate undergoes no rearrangement to sulfoxide even at high temperatures, the corresponding anisyl ester rearranges to p-anisyl trichloromethyl sulfoxide in hexane under mild conditions. Substitution of hexane by chloroform under similar conditions, lead to the formation of p-anisyl chloride and dichlorosulfine as main reaction products. This process is enhanced by the use of more polar solvents and higher temperatures. The conversion of trichloromethanesulfenate to chloride has also been observed with the benzyl and benzhydryl esters on heating in various solvents, though at very differing rates. Both rearrangements are suggested to take place by an ionization mechanism. Depending on the reaction conditions and nature of the substrate, the sulfenate anion can either recombine with the cation to give sulfoxide, or further dissociate to dichlorosulfine and chloride ion, which gives the benzyl chloride. The observation of an S_N1 type mechanism for rearrangement of sulfenates appears to be unique.     

Relaxation properties of some segmented polyurethane-CaCO3 composites. A Dielectric study

Dielectric relaxation in three segmented polyurethane-CaCO₃ composites was investigated between ?70°C and +150°C in the 300 Hz to 100 kHz frequency range. Two of the polymers contained a polyacetal-polyether soft segment, whereas the soft component of the third polymer was polypropylene oxide. The hard segments consisted of 4,4′-diphenyl methane diisocyanate in two cases and toluene-2,4-diisocyanate in the third case. In parallel studies two calorimetric relaxations, designated α and α′, were observed for each sample and were determined to be glass transitions of the soft and hard segments, respectively. In general, the transition temperatures decrease with increasing filler content. High frequency, low temperature permittivities increase while low frequency, high temperature AC conductivities generally decrease with increasing filler content. The shift in the transition temperatures can be explained using the adsorption theory of filler-polymer interactions and the densities of the samples. The interfacial polarization mechanism becomes important only above the α′ transition temperature and below 1 kHz.     

Low‐temperature controlled free‐radical polymerization of vinyl monomers in the presence of a novel cyclic dixanthate under γ‐ray irradiation

The free‐radical polymerization of methyl acrylate (MA) has been studied in the presence of a novel cyclic dixanthate under γ‐ray irradiation (80 Gy min^?1) at room temperature (～28 °C), ?30 °C, and ?76 °C respectively. The resultant polymers have controlled molecular weights and relatively narrow molecular weight distributions, especially at low temperatures (i.e., ?30 and ?76 °C). The polymerization control may be associated with the temperature: the lower the temperature is, the more control there is. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of poly(methyl acrylate) (PMA) samples shows that there are at least three distributions: [3‐(MA)_n‐H]⁺ cyclic polymers, [3‐(MA)_n‐THF‐H]⁺, and [3‐(MA)_n‐(THF)₂‐H]⁺ linear PMAs. The relative content of the cyclic polymers markedly increases at a lower temperature, and this may be related to the reduced diffusion rate and the suppressed chain‐transfer reaction at the low temperature. It is evidenced that the good control of the polymerization at the low temperature may be associated with the suppressed chain‐transfer reaction, unlike reversible addition–fragmentation chain transfer polymerization. In addition, styrene bulk polymerizations have been performed, and gel permeation chromatography traces show that there is only one cyclic dixanthate moiety in the polymer chain. This article is the first to report the influence of a low temperature on controlled free‐radical polymerizations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2847–2854, 2007