Synthesis and thermal properties of block copolyetheresters with poly(pentamethylene p,p′-bibenzoate) segments

The block copolyetheresters with hard segments of poly(pentamethylene p,p-bibenzoate) and soft segments of poly (tetramethylene ether) were prepared by melt polycondensation of dimethyl-p,p-bibenzoate, 1,5-pentanediol and poly (tetramethyene ether) glycol (PTMEG) with molecular weights of 650, 1000 and 2000. The results by NMR indicate that the polymer composition is determined by the charge molar ratio (x) of PTMEG to dimethyl-p,p-bibenzoate. The thermal transitions of the block copolyetheresters were investigated by DSC in combination with X-ray diffraction and polarized microscopy. Some block copolyetheresters exhibit a monotropic smectic phase due to the presence of the poly (pentamethylene p,p-bibenzoate) segments. As the molar content of PTMEG increases, the average sequence length of the polyester segments decreases, the isotropic-smectic transition temperature and the smectic order decrease accordingly. When x is as high as 0.3, the block copolyetheresters exhibit no liquid crystallinity.     

Syntheses and properties of polyimides based on bis(p-aminophenoxy)biphenyls

Three biphenyl unit-containing diamines,4,4-bis(p-aminophenoxy)biphenyl (III_a), 2,2-bis(p-aminophenoxy)biphenyl (III_b), and 3,3,5,5-tetramethyl-4,4-bis(p-aminophenoxy)biphenyl (III_c), were prepared by the chlorodisplacement ofp-chloronitrobenzene with 4,4-biphenol (I_a), 2,2-biphenol (I_b), and 3,3,5,5-tetramethyl-4,4-biphenol (I_c), respectively, giving the corresponding bis(nitrophenoxy) compounds II_a-c, followed by catalytic reduction with palladium (Pd) and hydrazine. Three series of polyimidesp-PI,o-PI, and Me-PI were prepared from diamines III_a-c and aromatic tetracarboxylic dianhydrides via a two-stage procedure that included ring-opening polyaddition to give poly(amic acid)s followed by thermal cyclodehydration to polyimides. The resultant three series of poly(amic acid)s had inherent viscosities of 1.09–2.83, 0.78–1.93, and 1.55–3.09 dL/g, respectively. Almost all the poly(amic acid)s could be solution-cast and thermally converted into transparent, flexible, and tough polyimide films. All the polyimides were characterized by solubility, tensile test, wide-angle X-ray scattering measurements, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Effects of the structures of aromatic diamines and dianhydrides on the properties of polyimides were investigated.     

Chemical modification of copoly(methylsilylene/1,4-phenylene) by Pt-catalyzed hydrosilation reactions with functionally substituted alkenes

Copoly(methyl-3-biphenoxypropylsilylene 1,4-phenylene), copoly(methyl-3-cyanopropylsilylene 1,4-phenylene), copoly(methyl-3-ethoxypropylsilylene 1,4-phenylene), copoly(methyl-3-phenoxypropylsilylene 1,4-phenylene), and copoly(methyl-4,7,10,13-tetraoxatetradecanylsilylene 1,4-phenylene) have been prepared by platinum-catalyzed hydrosilation graft reactions between poly (methylsilylene 1,4-phenylene) and appropriate functionally substituted alkenes. These polymers have been characterized by¹H,¹³C, and²⁹Si NMR as well as by FT-IR and UV-vis spectroscopy. The molecular weight distribution of these polymers has been determined by gel permeation chromatography (GPC), and their glass transition temperatures (T _e) by DSC.     

Thermotropic polyester: the influence of the spacer on the physical properties

Thermotropic polyesters prepared from series of 4,4-dihydroxy-,w-diphenoxy alkanes and 4,4-dichloroformyl-,w-diphenoxy alkanes are well known. The substitution of a methylenic spacer by an oxyethylenic spacer in the main chain of these polyesters drastically modifies their physical properties, particularly the mesogenic transition temperatures, as can be observed by DSC and thermooptical analysis. The thermal stability and the polymer solubility in common organic solvents of these polymers did not show a significant change. The physical properties of the two thermotropic polyesters prepared in diphenyl ether were evaluated.     

Synthesis and characterization of liquid crystalline poly(p-vinylbenzyl ether)s

Summary The synthesis and characterization of poly(p-vinylbenzyl ether)s containing 4-oxybiphenyl or 4-oxy-4-methoxybiphenyl mesogens or a 4-oxy-4-methoxybiphenyl mesogen which is connected to the benzyl ether group through one, two or three oligo(oxyethylene) units, are presented. The first two polymers exhibit a nematic mesophase while the last three a highly ordered smectic mesophase.     

Inhibition of male response of drugstore beetles to stegobinone by its isomer

Stegobinone, (2S, 3R, 1R)-2,3,-dihy dro-2,3,5-trimethyl-6-(1-methyl-2-oxobutyl)-4H-pyran-4-one, the sex pheromone of drugstore beetles (Stegobium paniceum L.), elicited the pheromonal response from the males of the species in our bioassay system; however, the synthesized diastereomeric mixture of this compound was actually inactive to the males. Although the stegobinone isolated from the beetles of this species had significant activity, its enantiomeric [(±)-2S,3R,1S-] and diatereomeric [(±)-2S,3S,1RS-] isomers were inactive. Adding the (±)-2S,3R,1S isomer to stegobinone significantly reduced the male response. Furthermore, the activity of Stegobinone vanished on keeping it at room temperature for two weeks. In such a stored stegobinone sample, the presence of 2S,3R,1S isomer, the inhibitory component, was confirmed. This isomer might be produced by C-1 epimerization during storage.     

Dynamic mechanical properties of some liquid crystalline polyacrylates

Summary The dynamic mechanical properties of some LC (nematic and smectic) polyacrylates with biphenyl mesogens with different spacers and tails are described. From plots of G and G against frequency and temperature the phase transitions could be clearly detected, in agreement with DSC analysis. Furthermore, the dynamic viscosities of the LC polyacrylates compared with an isotropic model polymer of similar stucture showed a strong shear rate and temperature dependence. Surprisingly it was found that the viscosity of the LC polymers was higher in the nematic phase than in the isotropic phase.     

Female-produced oviposition deterrents of the cigarette beetle,Lasioderma serricorne (F.) (Coleoptera: Anobiidae)

Oviposition deterrents of the cigarette beetle,Lasioderma serricorne, were isolated from its adult body extract and found to be identical to (2S,3R,1'S)-2,3-dihydro-3,5-dimethyl-2-ethyl-6-(l-methyl-2-oxobutyl)-4H-pyran-4-one (-serricorone) and its lR-epimer (-serricorone) by spectroscopic evidence. Serricorone was previously found as one of the minor sex pheromone components of the same insect, and hence indicating bi-functional nature. The presence of two isomers in the body was proved by careful treatment. Each of them exhibited the same level of oviposition deterring activity, which was less potent than the crude body extract at an increased concentration.     

Synthesis of new metal-containing side-chain monomers and polymers

New metal-containing vinyl monomers, hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hexyl-6-oxy-{4-[4-(4-ferrocenoyl phenyl)phenyl]benzoyloxy}methacrylate, and the corresponding homopolymers and random copolymers with hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate were synthesized. The compounds were characterized by¹H NMR; their thermal behavior was investigated by means of differential scanning calorimetry. Monomers and polymers containing the ferrocene unit melt at lower temperatures than those derived from the cyclopentadienyl managanese tricarbonyl moiety. The melting temperatures of the monomers and polymers ranged from 399 to about 515 K, Both monomers and polymers failed to exhibit mesogenic behavior. Values ofM _n,M _w,M _w/M _n, and degree of polymerization were obtained by gel permeation chromatography. TheM _n ranged from 16,500 for the copolymer containing hexyl-6-oxy-{4-[4-(4-ferrocenoyl phenyl)phenyl] benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio to 26,000 for the copolymer containing hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio.M _w/M _n ranged from 1.6 in the case of the copolymer containing hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio to 2.2 in the case of poly(hexyl-6-oxy{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate).     

Thermal transitions of liquid crystal polyesters: Poly(decamethylene-4,4′-diphenoxy terephthalate)

Summary The thermal transitions of liquid crystalline poly (decamethylene-4,4-diphenoxy terephthalate) have been studied by differential scanning calorimetry, X ray diffraction and thermoptical microscopy. At room temperature a three dimensional order and a smectic mesophase coexist. The crystal-smectic mesophase transition occurs at 240°C and at higher temperature, 250–260°C, a transition from smectic C to nematic has been observed, before the isotropic transition at 290°C. The no previously known smectic C-nematic transition has been detected by microscopy, observing bars and striated textures, and by X ray diffraction patterns obtained in the whole range of temperatures.     

The synthesis and characterization of a mesomorphic brush type polycarbosilane: poly[1,1-bis(4′-biphenyl)silabutane]

Summary Poly[1,1-bis(4-biphenyl)silabutane] (II) has been prepared by the anionic ring opening polymerization of 1,1-bis(4-biphenyl)silacyclobutane. II shows mesomorphic behavior by DSC. The¹³C NMR T₁ relaxation times have been measured. These are found to be smaller than those of poly(1,1-dimethylsilabutane)by an order of magnitude. This may result from interaction of the highly rigid biphenyl side chain moieties. The thermal stability of II is higher than that for other 1,1-disubstituted polysilabutanes.     

A solid-state electrochromic device based on complementary polypyrrole/polythiophene derivatives and an elastomeric electrolyte

A device was assembled using optically transparent glass electrodes and combining two complementary electrochromic polymeric materials, poly(4,4-dipentoxy-2,2-bithiophene) and poly(N,N-dimethyl-2,2-bipyrrole). As electrolyte we used an ionically conductive polymer; poly(epichlorohydrin-co-ethylene oxide) containing a lithium salt. The optical contrast in the visible/near infrared region, stability to repeated redox cycles and electrochromic efficiency are reported and discussed.     

The liquid crystalline state in organophosphazenes with biphenyl mesogenic groups

Hexakis[4-(4-decyloxy)biphenoxy]cyclotriphosphazene (HDBCTP), hexakis [4-(4-cyano)biphenoxy]cyclotriphosphazene (HCBCTP), poly{bis[4-(4-decyloxy) biphenoxy]phosphazene} (PDBP), and poly{bis[4-(4-cyano)biphenoxy] phosphazene} (PCBP) were synthesized from hexachlorocyclotriphosphazene or polydichlorophosphazene and the corresponding sodium alkoxide. Their phase transition and liquid crystalline state were then studied by differential scanning calorimetry (DSC) measurements and polarizing microscope observation. We found enantiotropic smectic C in HDBCTP between 431 and 457 K and monotropic nematic between 529 and 488 K in HCBCTP only in the cooling process. No mesomorphic state was found in PDBP and PCBP.     

Preparation and thermotropic properties of copoly(4,4′-biphenylene sebacate-co-eicosanedioate)s

Summary A series of thermotropic copoly(4,4-biphenylene sebacate-co-eicosanedioate)s were prepared by melt polycondensation of 4,4-biphenylene diacetate, sebacic acid and eicosanedioic acid. Their thermal transitions and liquid crystalline properties were investigated by DSC and polarized micrrocope. The copolyesters were found to exhibit a smectic phase, but no nematic phase was observed upon cooling. The smectic-isotropic transition temperature decreased as the content of eicosanedioate unit increased, and the corresponding transition heat did not change to a great extent. However, the crystalline-smectic transition temperature showed an eutectic behavior, and the crystalline-smectic transition heat was depressed considerably after copolymerization. The X-ray diffraction data of the copolyesters after thermal treatment were measured and compared with the thermal properties measured by DSC.     

Microhardness and DSC measurements on liquid crystalline poly(diethylene glycolp,p′-bibenzoate) as a function of the ageing time

Summary The ageing process of the liquid crystalline glass of poly(diethylene glycolp,p-bibenzoate), PDEB, has been studied by differential scanning calorimetry and microhardness measurements. The experiments have been performed on a sample of PDEB aged at 36±C during different times. The process was found to be rather fast at that temperature, and the results from both techniques are compared.     

Small-angle synchrotron study of liquid crystalline poly[oxybis(trimethylene) p,p′-bibenzoate]

Summary Small-angle synchrotron experiments have been performed in two samples of poly[oxybis(trimethylene) p,p-bibenzoate], PDTMB. Owing to the very slow transformation of the mesophase of this polymer into the crystal, only the liquid crystalline phase is present in a PDTMB sample quenched from the melt, while about 30% crystallinity is found in the annealed specimen. The results indicate that the layer spacing peak for the mesophase is very close to a crystal diffraction. This seems to be a general fact in thermotropic polybibenzoates. Moreover, no long spacing has been detected in the quenched sample. On the contrary, the annealed specimen exhibits a long spacing centered at about 16 nm, corresponding to a rather small crystal thickness.     

New phenothiazine-containing monomers and polymers

Summary Three new phenothiazine-containing electrono-donor monomers: methacryloyl-2-hydroxyethyl-2-(N-phenothiazinyl)propionate (i) acryloyl-2-hydroxyethyl-2-(N-phenothiazinyl) propionate (ii) and 2-(N-phenothiazinyl) propionic acid vinyl ester (iii) were synthesized and radically polymerized. The ionization potentials of poly(i), poly(iii) and of the model for the structural unit of the acrylic polymers: acetyl-2-hydroxyethyl-2-(N-phenothiazinyl) propionate determined with two small acceptors were discussed in terms of sterical hindrances.     

Comparison of some 4- and 4,4′-substituted derivatives of stilbene for their reactivities towards the benzoyloxy radical

Summary 4-Fluoro- and 4,4-difluorostilbene are similar in their reactivities towards the benzoyloxy radical; a similar conclusion has been reached in respect of 4-chloro- with 4,4-dichlorostilbene and 4-phenyl-with 4,4-diphenylstilbene. These results have been obtained by consideration of the numbers of benzoate and phenyl end-groups in poly (methyl methacrylate) made using benzoyl peroxide in the presence of the appropriate derivative of stilbene.     

Synthesis and characterization of poly(vinylether)s with pendant mesogenic groups

Two different methods of synthesis were examined for the preparation of poly(alkylvinylether)s with pendant 4-cyano-4-oxy-biphenyl mesogenic groups attached to side chains of different length: a) anchoring of the mesogenic group onto an alkylvinylether monomer followed by polymerization or b) synthesis of the corresponding poly(chloroalkylvinylether)s and chemical substitution of the pendant chlorine by the mesogenic groups. Polymerization were performed with initiating systems based on activated iodide. Much better control of MW and MWD of the final polyvinylether chains was obtained when process b) was applied. Polymers with 2 and 4 carbons in the spacer do not show liquid crystalline properties. It is only with polymers having six carbon atoms in the spacer that mesophases were observed. Those issued from process b) give two distinct mesophases: a smectic A phase in the high temperature range and a smectic C phase for the low one. Polymers synthetized from process a) present only the smectic A phase. The effects of molecular weights and molecular weight distributions on the liquid crystalline properties have been examined and are discussed.     

Shape-Selective Alkylation of Biphenyl over H-[Al]-SSZ-31 with Propylene

Isopropylation of biphenyl (BP) over [Al]-SSZ-31, a large-pore, one-dimensional zeolite has been studied. Effects of temperature, pressure and SiO₂/Al₂O₃ ratio were examined. SSZ-31 was found to be an active catalyst in the isopropylation of biphenyl with propylene. The selectivity for 4-isopropylbiphenyl (4-IPBP) and 4,4-diisopropylbiphenyl (4,4-DIPB) was high among isopropylbiphenyl (IPBP) and diisopropylbiphenyl (DIPB) isomers, respectively, indicating SSZ-31 shows shape-selective catalysis. The selectivity for 4,4-DIPB decreased with temperature increase; correspondingly the selectivity for thermodynamically more stable isomers (3,3- and 3,4 DIPB) increased with temperature. The yield of IPBP isomers decreased while that of DIPB isomers increased with temperature increase. Pressure showed less effect on conversion; however, increase in pressure suppresses the isomerization of 4,4-DIPB to 3,3- and 3,4-DIPB. Conversion decreased with increase in SiO₂/Al₂O₃ ratio. At low SiO₂/Al₂O₃ ratio of 136, relatively high triisopropylbiphenyl (TriIPB) isomers were formed in bulk products and their amount decreased with increase in SiO₂/Al₂O₃ ratio.