Preparation of ester terminated poly(alkyl vinyl ether) oligomers and block copolymers using a combination of living cationic and group transfer polymerization

Summary This paper reports the synthesis and characterization of new, functionalized poly(alkyl vinyl ether) oligomers, and block copolymers containing poly(alkyl vinyl ether) and poly(methyl methacrylate). Using the HI/ZnI₂ initiating system in nonpolar solvents (hexane, toluene) at -15 °C, both monofunctional and difunctional poly(alkyl vinyl ether) oligomers of predicted molecular weights precisely terminated with ester end groups have been prepared. Novel diblock copolymers comprised of poly(methyl methacrylate) and poly(alkyl vinyl ether) have also been synthesized using a combination of living cationic and living group transfer polymerization (GTP) techniques.     

Thermal crosslinking of poly(methyl methacrylate-co-N,N-dimethylaminopropylacrylamide)

Summary Copolymers of methyl methacrylate(MMA) with N,N-dimethylaminopropylacrylamide (DMA) were heated at various temperatures, and their thermal crosslinking was investigated. A copolymer with a compsition of [MMA]/[DMA] =3 became completely insoluble in chloroform when heated at 180°C for 5 minutes or at 150°C for 20 minutes. Other copolymers containing less than 5 mol % DNA also crosslinked when heated at 170°C for 30 minutes. A mixture of polyMMA with N,N-dimethylaminopropylbenzamide also crosslinked when heated at 170°C. A copolymer of styrene with DMA also crosslinked when heated at above 140°C although the crosslinking was much slower than that of poly(MMA-co-DMA). The formation of imide linkages is proposed as the crosslinking mechanism.     

Poly(thioether imide)s via chloro-displacement polymerization

Summary Thioether containing polyimides were prepared by displacement of chlorine groups from substituted imides by aromatic and aliphatic sulfur nucleophiles. The allaromatic monomers and polymers had poor solubility which led to precipitation during synthesis and low molecular weight polymers. However, these polymers were thermally stable up to 400 °C and had T_g's ranging from 212 °C to 233 °C. Poly(thioether imide)s prepared from 1,3-propanedithiol and 2-mercaptoethyl sulfide had good solubility but lower thermal stability, showing TGA loss onset temperatures of 297 °C and 298 °C, respectively.     

Copolymerization behavior and properties of dimethacrylate-styrene networks

Dimethacrylate oligomers diluted with styrene (commonly known as vinyl ester resins) are important matrix resins for fiber-reinforced composites used in construction, marine craft, and transportation vehicles. These comonomers react via free radical copolymerization to yield void-free thermosets. The inter-relationships among copolymerization kinetics, physical properties of the networks, and cure temperatures for a 700 g/mol dimethacrylate oligomer with systematically varied styrene concentrations were investigated. FTIR was used to monitor the reactions of the carbon-carbon double bonds of the methacrylate (943 cm⁻¹) and styrene (910 cm⁻¹). Reactivity ratios were determined via a non-linear method at four cure temperatures. The data were analyzed using the integrated form of the copolymerization equation and assuming a terminal reactivity model to predict copolymer compositions throughout the reactions. The results indicated that at early conversion more styrene was incorporated into the networks at lower cure temperatures. The experimental vinyl ester-styrene network compositions agreed well with those predicted by the integrated copolymer equation at early and intermediate conversion. Mechanical properties of dimethacrylate-styrene networks were determined for materials cured at room temperature and at 140 °C. Materials cured at room temperature were tougher and had lower rubbery moduli than those cured at 140 °C.     

Thermal decomposition of poly(tetramethyloxydisilaethylene)

Thermal decomposition of poly[oxybis(dimethylsilylene)] having chains terminated with trimethylsiloxy groups was studied by thermogravimetry, pyrolysis-mass spectrometry, and infrared spectroscopy. The polymer is thermally less stable than poly(dimethylsiloxane). Depolymerization occurs at temperatures of 250–350°C, although this process also takes place at lower temperatures. The depolymerization produces cyclic oligomers of general formula [(Me₂Si)₂O] _n , with predominant formation of the oligomern=2. The depolymerization is accompanied by processes which are referred to as restructurization because they change the structure of the polymer backbone. Decomposition may lead also to the formation of branching points. The shape of the thermograms taken under isothermal conditions is in agreement with an unzipping mechanism for depolymerization involving random initiation. Excluding the short initial period of the process, the unzipping is terminated at a restructurization point. A low activation energy points to initiation induced by electron transfer, presumably involving traces of contaminant. At higher temperatures, 350–600°C, loss of organic parts of the polymer takes place along with further restructurization. At higher temperatures the polymer was also found to undergo easily oxygenation of its backbone with atmospheric oxygen, which leads to the formation of siloxane groups.     

Formation of fullerenes by pyrolysis of perchlorofulvalene and its derivatives

In a retro-synthetic approach, [60]fullerene might be accessible by condensing six fulvalene fragments. In order to explore the potential of such a route for direct synthesis of [60]fullerene we have investigated the pyrolysis of perchlorofulvalene (PCF). Low temperature pyrolysis of PCF at 250 °C resulted mainly in the formation of dimers, trimers, tetramers and products of subsequent intramolecular condensation of these oligomers. Increasing the temperature to 300-350 °C leads to the formation of perchlorinated polynuclear aromatic hydrocarbons. Pyrolysis at 400-450 °C gives a cross-linked polymer structure which is the result of intermolecular condensation of the polynuclear aromatic intermediates. Pyrolysis at higher temperatures (>500 °C) mainly leads to graphite. It was found that the two-step pyrolysis of PCF (heating first at 450 °C, after that at 750 °C) yielded a fullerene containing soot via an intermediate polynuclear aromatic net. High temperature rearrangement of the latter gave fullerenes C₆₀ and C₇₀. The best results were obtained when a PCF oligomer obtained by Ullmann condensation was used as a precursor. By two-step pyrolysis and further high vacuum sublimation of the soot the fullerenes C₆₀ and C₇₀ were obtained in extractable amounts.     

Synthesis and characterisation of novel methyl methacrylate-2-(dimethylamino)ethyl methacrylate copolymer salts containing polymerisable anions

A series of copolymers containing different ratios of methyl methacrylate and 2-(dimethylamino)ethyl methacrylate has been synthesised by conventional free radical polymerisation. These copolymers have been converted into a series of novel salts by reaction with the acid monomers, methacrylic acid, methacryloyloxyethyl phosphate and vinyl phosphonic acid. The copolymers and the corresponding salts have been characterised fully by a range of spectroscopic and thermal analysis techniques. The nature of the salt has a characteristic effect on the thermal degradation of the polymer. The presence of the phosphorus monomers leads to formation of residual char, even at temperatures as high as 1000 °C.     

Thermoreversible cross-linking of maleated ethylene/propylene copolymers with diamines and amino-alcohols

Maleated ethylene/propylene copolymers (MAn-g-EPM) were thermoreversibly cross-linked using diamines and amino-alcohols. Covalent cross-links are formed via the equilibrium reaction of the grafted anhydride groups with di-functional cross-linkers containing combinations of primary (1°) and secondary (2°) amines and alcohols, while a shift of the equilibrium at elevated temperatures may result in their (partial) removal. Materials cross-linked with cross-linkers containing two 2° amine groups (2°-2°) and 2° amine and alcohol groups (2°-OH) are repeatedly processable via compression molding without chemical changes, which is an improvement in reversibility compared to the previously-studied cross-linking reactions with diols, for which irreversible side reactions limited the reversibility to some extent. The use of 1° amine groups results in materials that are not reprocessable via compression molding, due to irreversible imide formation. The 2°-2° and 2°-OH materials have higher levels of cross-linking after remolding than the diol-cross-linked MAn-g-EPM, which results in significant differences in rubber properties. Fourier transform infrared (FTIR) spectroscopy suggested that the reprocessability of these materials is caused by a continuous, dynamic exchange between cross-linked and free groups. Finally, the use of cross-linkers containing 3° amine groups results in the formation of ionic interactions. These materials are easily reprocessable at temperatures as low as 125 °C and have significantly different properties than the covalently cross-linked materials, due to the occurrence of ion hopping.     

Polymers containing formamidine groups

Summary New aromatic polymers containing formamidine groups were prepared by high temperature solution polycondensation of triethyl orthoformate with various aromatic diamines. The resulting polyformamidines were characterized by elemental analysis, IR' and ¹H NMR spectroscopy, viscosity measurements, thermogravimetry, DSC- and WAXS measurements. With few exceptions aromatic polyformamidines show excellent solubility in polar solvents and strong acids, but they were gradually decomposed in extended contact with moisture. Polyformamidines containing rigid para structures are well crystallizing materials, which was proved by WAXS investigations. Glass transition temperatures in the range of 62 – 163°C were observed for semicrystalline or amorphous polymers. All aromatic polyformamidines are thermally stable in nitrogen up to 300°C.     

Synthesis and properties of boron-containing soybean oil based thermosetting copolymers

The first example of boron-containing soybean oil based copolymers was prepared from soybean oil, styrene, divinylbenzene and 4-vinylphenyl boronic acid by cationic polymerization using boron trifluoride etherate as initiator. Soxhlet extraction and NMR spectroscopy indicate that the copolymers consist of a crosslinked network plasticized with varying amounts of oligomers and unreacted oil. The thermal degradation mechanism was studied and the thermal, dynamomechanical and flame retardant properties of these materials were examined. Thermosets with glass transition temperatures ranging from 43 to 60 °C, which are thermally stable below 350 °C and with LOI values from 23.7 to 25.6 were obtained. The LOI tests indicate that the flame retardant properties of vegetable oil can be improved by adding boron covalently bonded to the polymer.     

Cationic oligomerization of 3-methylene-p-menth-4(8)-ene and 2-methyl-3-methylene-5-isopropylbicyclo [3.1.01,5] hexane

Summary The title monomers were synthesized via Wittig reaction from thujone and pugelone. The monomers were found to react rapidly with cationic initiators at temperatures from -15° to 22°C. The products of these reactions were found to be low molecular weight oligomers. The reaction temperature, presence of solvent or initiator type and concentration seemed to have some effect on the molecular weights of the products obtained.     

Characteristics of nanosized Bi-based glass powders prepared by flame spray pyrolysis as transparent dielectric layer material

Bi-based glass powders with particle size of 34 nm were prepared by high-temperature flame spray pyrolysis. The glass transition temperature (T_g) of the powders was 442 °C. Dielectric layers fired at temperatures of 480 and 500 °C contained voids, while those fired at temperatures above 540 °C had clean surfaces and no voids. The dielectric layers sintered at temperatures of 560 and 580 °C had transmittances of 70% in the visible range. Further, it was observed that the dielectric layers formed from the nanosized glass powders obtained from spray solutions containing excess boron had higher transmittances (80% in the visible range at a sintering temperature of 580 °C) than the layers formed from spray solutions containing stoichiometric amounts of boron.     

Mechanical properties of porous carbon material: Woodceramics

The mechanical properties of Woodceramics which were made from medium-density fiberboard have been investigated with special reference to the effect of burning temperature on their bending Young's modulus and bending strength. Woodceramics made from beech wood have also been tested to clarify the compressive strength anisotropy, and the role of phenol resin impregnation in strengthening the beech based charcoal.The bending Young's modulus hardly varies for burning temperatures between 300 and 500°C, but it improves remarkably for burning temperatures between 500 and 800°C. The bending strength degrades with temperature for burning temperatures between 300 and 500°C, but it improves remarkably with increasing temperature of burning between 500 and 800°C. The bending Young's modulus and bending strength gradually degrade with temperature for burning temperatures at and above 2000°C.The compressive strength of beech wood burned at 800°C in the longitudinal direction is greater than that in the radial direction, which in turn is greater than that in the tangential direction; this reflects the anisotropy of wood. Woodceramics made from beech wood have a compressive strength superior to beech charcoal in any of the following three directions: 4.5 times in the longitudinal direction, 3.4 times in the radial direction, and 2.0 times in the tangential direction. Both for beech charcoal and beech Woodceramics, brittle fracture is brought about by the buckling of cell wall in compression along the longitudinal direction but by the bending of cell wall in the compression along radial and tangential direction.     

Structure and properties of highly stereoregular isotactic poly(methyl methacrylate) and syndiotactic poly(methyl methacrylate) blends treated with supercritical CO2

The structure and properties of highly stereoregular isotactic poly(methyl methacrylate) (it-PMMA) and syndiotactic poly(methyl methacrylate) (st-PMMA) blends with crystalline stereocomplex formed by supercritical CO₂ treatment at temperatures ranging from 35 to 130 °C were investigated by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and dynamic mechanical analysis (DMA) measurements. The melting temperature, T_m, and the heat of fusion, ΔH_m, had maximum values at about 200 °C and 25 J/g, respectively. The degree of crystallinity evaluated by WAXD ranged in value from 32 to 38%. The fringed-micellar stereocomplex crystallites were formed in case of treatment temperatures below 90 °C, and the orderliness perpendicular to the helix axis of the fringed-micellar crystallites was considered to be increased with increasing treatment temperature. In case of treatment temperature of 130 °C, the fringed-micellar crystallites and the lamellar crystallites with high orderliness parallel to the helix axis coupled with the perpendicular orderliness were formed, and the respective double endothermic peaks, T_m¹ and T_m³, were observed in DSC due to the melting of the two kinds of stereocomplex crystallites. The it-PMMA/st-PMMA blends containing the fringed-micellar crystallites maintained high values of storage modulus, E′, up to higher temperature compared with the amorphous blends. The E′ of the blend treated with CO₂ at 130 °C decreased twice at temperatures corresponding to T_m¹ and T_m³.     

Co-pyrolysis of polymethyl methacrylate with brown coal and effect on monomer production

Pyrolysis capillary gas chromatography has been applied to the study of the co-pyrolysis of polymethyl methacrylate (PMMA) with Slovakian brown coal with the aim of finding pyrolysis conditions yielding a maximum amount of methyl methacrylate (MMA). Effects of pyrolysis temperature and PMMA-coal weight ratios were investigated. Capillary gas chromatography coupled with mass spectrometric detector (cGC-MS) was used for MMA identification. The highest yield of MMA in the pyrolysate was obtained at 750 °C. The optimal PMMA-coal weight ratio for maximum MMA production lies in the interval 0.5 mg PMMA and 0.6-0.8 mg brown coal with an MMA yield of 64%. Coal addition to the sample affects species recombination in gaseous phase, augments MMA production at higher temperatures and eliminates degradation products of PMMA and coal pyrolysis. Different conversion diagrams are characteristic for thermal degradation of single PMMA and in the mixture with coal. Detailed mechanism of synergetic effects arisen during co-pyrolysis are not yet known. It was also found that lower pyrolysis temperatures are more suitable to study degradation mechanism and kinetics while higher temperatures are more applicable for identification purposes. MMA decomposes completely at 900 °C.     

Thermal stability of poly(styrene-b-methyl methacrylate) and poly(styrene-b-ethylene-co-1-butene-b-methyl methacrylate)

Summary The thermal stability of poly(styrene-b-methyl methacrylate) diblock copolymers (= P(S-b-MMA)) and poly(styrene-b-ethylene-co-1-butene-b-methyl methacrylate) triblock copolymers (=P(S-b-EB-b-MMA)) was investigated. Well-defined high molecular weight block copolymers with narrow molecular weight distribution (MWD) were molded at different temperatures in vacuum and the alteration of the MWD was sensitively monitored by gel permeation chromatography (GPC). Up to 240°C P(S-b-MMA) shows almost no broadening of the MWD. At higher temperatures low molecular weight polystyrene-rich portions are formed. The number average molecular weight (M_n) is strongly reduced. P(S-b-EB-b-MMA) triblock copolymers show broadening of the MWD to higher and lower molecular weights at elevated temperatures, probably caused by chain scission and linking reactions of the EB block. M_n remains approximately constant. Up to 240°C the broadening of the MWD is not very pronounced. In comparison to unhydrogenated P(S-b-B-b-MMA) triblock copolymers, the thermal stability of P(S-b-EB-b-MMA) is greatly enhanced.     

Synthesis and properties of UV-curable hyperbranched polyurethane acrylate oligomers containing carboxyl groups

Using step by step polymerization process, the first- and second-generation hyperbranched polyesters were synthesized with N,N-diethylol-3-amine methylpropionate as branched monomer and pentaerythrite as a core molecule. The second-generation hyperbranched polyurethane acrylate oligomers containing carboxyl groups were obtained by further reacting with semiadduct urethane monoacrylate and maleic anhydride. The structures of the oligomers were investigated with elemental analysis, FT–IR, and NMR. UV–Vis spectra results showed that the oligomers had sharp absorption bands at about 207 nm. The glass transition temperatures were investigated by differential scanning calorimetry and showed in the range of −44.96 to −19.83 °C. Gel permeation chromatograph was used to observe the molecular weights and polydispersities of the oligomers. UV-curing properties were characterized by FT–IR with different curing time. In addition, the solubilities and viscosity of the oligomers were also examined.     

Metal polymers

Summary Styrene-co-butyl methacrylate colloids were obtained by codeposition at 77 K of the monomers with several metals such as Pd, Au, Ag, Cu, Zn, Cd, Ga, In, Ge, Sn, Sb and Bi. The colloids were copolymerized with different amounts of initiator (BPO) at 65°C for 3.0 h and a wide range of viscosity average molecular weights (Mv, 10⁴–10⁵ g/mol) were obtained depending upon the metal used. The metal colloid concentration and stability are reported. A medium particle size of 60-244 Å comonomer colloids was found. The thermal stability and metal composition are also described. The copolymers are stable even at 380°C, Ga- poly(styrene-co-butyl methacrylate) being the most stable with 418°C. The metal content is ranging between 0.10 and 2.26% w/w for the highest MW fraction and between 0.20 and 2.41% w/w for the lowest MW fraction. Copolymers with different colors were obtained depending on the metal used.     

Acrylated polyurethanes by reactive extrusion

A one-step acrylated polyurethanes prepolymers synthesis by reactive extrusion and bulk reaction is discussed.These oligomers are obtained by a simultaneous reaction of MDI, polycaprolactone and hydroxyethyl-acrylate. In order to obtain a high reaction conversion within the extruder, tin laurate catalyst was used at 90°C. In these conditions, an appropriate radical initiator can be introduced during the extrusion without double bond polymerization. Comparing bulk and reactive extrusion prepared products, oligomer Tg were respectively 18°C and +8°C for oligomers and +18°C and +27°C for the issued networks.     

Effect of temperature on the monomer reactivity ratios of 2-hydroxypropyl methacrylate with methyl acrylate and methyl methacrylate

Summary 2-Hydroxypropyl methacrylate (2-HPMA) has been copolymerized with methyl acrylate (MA) and methyl methacrylate (MMA) in bulk at temperatures between 60 and 100°C using benzoyl peroxide as initiator. The compositions of copolymers have been determined by hydroxyl content; the reactivity ratios have been calculated by Kelen Tüdös method. The intrinsic viscosities and thermal behaviour of the copolymers were also studied.