Synthesis and characterization of new optically active poly(amide-imide)s containing 1,3,4-oxadiazole moiety in the main chain

Six new optically active poly(amide-imide)s were synthesized by poly condensation reaction of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (8) with six chiral N,N′-(bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic)-bis-l-amino acids (3a–f) in a medium consisting of N-methyl-2-pyrrolidone (NMP), triphenylphosphite (TPP), calcium chloride (CaCl₂), and pyridine. Chiral N,N′-(bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic)-bis-l-amino acids (3a–f) were obtained by the reaction of bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (1) with two equimolar of l-alanine (2a), l-valine (2b), l-leucine (2c), l-isoleucine (2d), l-phenyl alanine (2e), and l-2-aminobutyric acid (2f) in acetic acid. The poly condensation reaction produced a series of novel poly(amide-imide)s (9a–f) in high yield and with inherent viscosities between 0.30 and 0.52 dL/g. The resulting polymers were characterized by elemental analysis, viscosity measurement, solubility testing, thermo-gravimetric analysis (TGA), ¹H-NMR, and FT-IR techniques.     

Gas permeation properties of poly(2,5-dialkyl-p-phenyleneethynylene) membranes

Dipropynylbenzenes with alkyl groups (CH₃C ≡ CRC₆H₂RC≡CCH₃, R=n-C₆H₁₃, n-C₈H₁₇, n-C₁₀H₂₁, 1a–c, respectively) were polymerized with Mo(CO)₆ to afford solvent-soluble poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c). The polymers (2a–c) had high molecular weight over 3×10⁴, and gave free-standing membranes by solution casting method. According to thermogravimetric analysis (TGA), these poly(p-phenyleneethynylene)s showed high thermal stability (T₀ ≥380 °C). The densities of membranes of poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c) were 0.936–0.965, and their fractional free volume (FFV) were relatively large (ca. 0.14–0.15). The oxygen permeability coefficients (PO₂) of membranes of 2a–c were 4.88, 7.06, and 16.6 barrers, respectively.     

Radical polymerization of (trimethylsilylethynyl)styrene and thermal properties of polystyrene with ethynyl group

The radical polymerizations of 2-, 3-, and 4-(trimethylsilylethynyl)styrenes (1 a – c) and copolymerizations of 1 a – c (M₁) with styrene (M₂) have been studied. Copolymerization parameters were determined as r₁ = 1.22 and r₂ = 0.54 for 1 a, ₁ = 1.10 and r₂ = 0.90 for 1 b, and r₁ = 1.42 and r₂ = 0.38 for 1 c. The deprotection of the trimethylsilyl groups in poly[(trimethylsilylethynyl)styrene] (2 a – c) and poly[(trimethylsilylethynyl)styrene-co-styrene] (4 a – c) using (C₄H₉)₄NF smoothly proceeded to yield poly(ethynylstyrene) (3 a – c) and poly(ethynylstyrene-co-styrene) (5 a – c), respectively, which underwent curing reactions at elevated temperature to form crosslinking polystyrenes. Received: 31 March 1997/Revised: 2 June 1997/Accepted: 3 June 1997     

Synthesis of Poly(propargyl esters) with Rhodium Catalysts and Their Characterization

Summary Propargyl esters (HC≡CCH₂OC(=O)R; 1: R = n-C₅H₁₁, 2: R = CH₃, 3: R = CHBrCH₃, 4: R = C₆H₅, 5: R = C(C₆H₅)₃) were polymerized by using (nbd)Rh⁺(η⁶-Ph-B^-Ph₃) (nbd = 2,5-norbornadiene) to produce poly(1)–poly(5) with molecular weights in the range of M_n = 4,900–40,000. Poly(1), poly(3) and poly(4) were readily soluble in common organic solvents such as toluene, THF and CHCl₃, and poly(2) showed similar solubility behavior except that it was insoluble in THF. Poly(5) did not dissolve in any organic solvent. Poly(1) was yellow oil, while poly(2)–poly(5) were yellow solids. Poly(1)–poly(4) exhibited UV-vis absorptions in a range of 300–425 nm, which are attributed to the conjugation of the main chain. All the polymers were thermally stable up to 150–200 °C.     

Synthesis and characterization of poly(meth)acrylates containing tricyanocyclopropane ring for piezoelectric applications

Summary p-(2,2,3-Tricyano-3-carbomethoxycyclopropyl)phenoxyethyl acrylate (5a) and p-(2,2,3-tricyano-3-carbomethoxycyclopropyl)phynoxyethyl methacrylate (5b) were prepared by the reactions of bromomalononitrile with methyl p-(2-acryloyloxyethoxy)benzylidene-cyanoacetate (4a) and methyl p-(2-methacryloyloxyethoxy)benzylidenecyanoacetate (4b), respectively. Monomers 5a and 5b were polymerized with free-radical initiators to obtain the polymers with multicyanocyclopropane functionalities in the pendant group. The resulting polymers 6a and 6b were soluble in acetone and the inherent viscosities were in the range of 0.20–0.25 dL/g. Solution-cast films showed T _g values in the range of 130–150°C and piezoelectric coeffcients (d₃₁) of the poled films were 1.5–1.6 pC/N, which are acceptable for piezoelectric device applications. Received: 28 April 2000/Accepted: 26 June 2000     

Synthesis and gas permeability of poly(<Emphasis Type="Italic">p</Emphasis>-phenyleneethynylene)s having bulky alkoxy or alkyl groups

Dipropynylbenzene with branched alkoxy and alkyl groups [CH₃C≡CRC₆H₂RC≡CCH₃, R = 2-methylpropoxy (1a), 3-methylbutoxy (1b), 4-methylpentoxy (1c), cyclohexylmethoxy (1d), 2-ethylhexoxy (1e), 2-octoxy (1f), 2-ethylhexyl (1g), and 2-octyl (1h)] were polymerized with Mo(CO)₆ in the presence of 4-(trifluoromethyl)phenyl to afford poly(2,5-di(alkoxy or alkyl)-p-phenyleneethynylene)s (2a–h). Polymer 2a was insoluble in any solvents, but the other polymers (2b–h) were soluble in common organic solvents. The polymers with relatively long side chains (2e–h) had high molecular weight over 1.6 × 10⁴ and gave free-standing membranes by solution-casting method. The densities of membranes of 2e–h were 0.914–0.998, and their fractional-free volume values were relatively large (0.094–0.158). The oxygen permeability coefficients of membranes of 2e–h were 18.4, 12.7, 4.85, and 19.3 barrers, respectively. It was found that poly(p-phenyleneethynylene) with 2-octyl side groups, which have the branch at the nearest position from main chain, exhibited the highest gas permeability.     

Synthesis and surface properties of chemodegradable anionic surfactants: Diastereomeric (2-n-alkyl-1,3-dioxan-5-yl) sulfates with monovalent counter-ions

Sodium, potassium and ammonium cis- and trans-(2-n-alkyl-1,3-dioxan-5-yl) sulfates 6–8 (alkyl: n-C₉H₁₉, 6a–8a, and n-C₁₁H₂₃, 6b–8b) were synthesized in a reaction of aliphatic aldehydes 1a,b with glycerol 2 followed by separation in high yields of individual geometric isomers of cis-and trans-2-n-alkyl-5-hydroxy-1,3-dioxanes, cis-3a,b and trans-3a,b, followed by sulfation with sulfur trioxide-pyridine complex, and finally neutralization with NaOH, KOH, and NH₄OH, respectively. Physical data of the compounds and some surface properties of 2-n-nonyl derivatives, such as critical micelle concentration (CMC), effectiveness of aqueous surface tension reduction (Π_CMC), surface excess concentration Γ_CMC, and the surface area demand per molecule (A_CMC), were determined. It was shown that the surface activity of these compounds is influenced both by their geometric structure and by the monovalent counter-ion.     

Synthesis of poly(ethyl vinyl ethers) containing two dipolar electronic systems and their properties

Summary 5-Nitro-2-(2′-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 5-nitro-2-(2′-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3-nitro-4-(2′-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl 3-nitro-4-(2′-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of 5-nitro-2-(2′-vinyloxyethoxy)benzaldehyde (1) and 3-nitro-4-(2′-vinyloxyethoxy)benzaldehyde (3) with malononitrile or methyl cyanoacetate, respectively. Vinyl ether monomers 2a-b and 4a-b were polymerized with boron trifluoride etherate as a cationic initiator to yield poly(vinyl ethers) 5-6 having nitrooxybenzylidenemalononitrile and nitrooxycyanocinnamate, which is effective chromophore for second-order nonlinear optical applications. Polymers 5-6 were soluble in common organic solvents such as acetone and DMSO. T _g values of the resulting polymer were in the range of 70–81°C. Electrooptic coefficient (r₃₃) of the poled polymer films were in the range of 19–27 pm/V, which was improved by introducing of nitro group. Polymers 5–6 showed a thermal stability up to 300°C in TGA thermograms, which is acceptable for NLO device applications. Received: 24 November 1998/Revised version: 19 January 1999/Accepted: 29 January 1999     

Enantiospecific Effect of Pulegone and Pulegone-Derived Lactones on Myzus persicae (Sulz.) Settling and Feeding

The effect of pulegone chiral center configuration on its antifeedant activity to Myzus persicae was examined. Biological consequences of structural modifications of (R)-(+)- and (S)-(−)-pulegone, the lactonization, iodolactonization, and incorporation of hydroxyl and carbonyl groups were studied, as well. The most active compounds were (R)-(+)-pulegone (1a) and δ-hydroxy-γ-spirolactones (5S,6R,8S)-(−)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2-one (5b) and (5R,6S,8S)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2-one (6b) derived from (S)-(−)-pulegone (1b). The compounds deterred aphid probing and feeding at preingestional, ingestional, and postingestional phases of feeding. The preingestional effect of (R)-(+)-pulegone (1a) was manifested as difficulty in finding and reaching the phloem (i.e., prolonged time preceding the first contact with phloem vessels), a high proportion of probes not reaching beyond the mesophyll layer before first phloem phase, and/or failure to find sieve elements by 20% of aphids during the 8-hr experiment. The ingestional activity of (R)-(+)-pulegone (1a) and hydroxylactones 5b and 6b resulted in a decrease in duration of phloem sap ingestion, a decrease in the proportion of aphids with sustained sap ingestion, and an increase in the proportion of aphid salivation in phloem. δ-Keto-γ-spirolactone (5R,8S)-(−)-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2,6-dione (8b) produced a weak ingestional effect (shortened phloem phase). The postingestional deterrence of (R)-(+)-pulegone (1a) and δ-hydroxy-γ-spirolactones (5R,6S,8R)-(+)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]-decan-2-one (5a), 5b, (5S,6R,8R)-6-hydroxy-4,4,8-trimethyl-1-oxaspiro[4.5]decan-2-one (6a), 6b, and δ-keto-γ-spirolactone 8b prevented aphids from settling on treated leaves. The trans position of methyl group CH₃–8 and the bond C5–O1 in lactone 6b appeared to weaken the deterrent activity in relation to the cis diastereoisomer (5b).     

Two Novel Ceramides with a Phytosphingolipid and a Tertiary Amide Structure from <Emphasis Type="Italic">Zephyranthes candida</Emphasis>

Two novel ceramides, Candidamide A (1) with a phytosphingolipid structure, and Candidamide B (2) with a tertiary amide structure, together with 12 known compounds (3–14) have been isolated from the bulbs of Zephyranthes candida, The structures of 1 and 2 have been elucidated to be 1,3,5,6-tetrahydroxy-2-(2′-hydroxytetracosanoyl amino)-8-(E)-octadecadiene (1) and (2S,3S,4R,8E,2′R)-2-[N-(2′-hydroxyoctadecanoyl)-N-(1′′,2′′-dihydroxyethyl)-amino]-8-hexacosene-1,3,4-triol (2) on the basis of spectroscopic evidence including IR, MS, NMR (¹H-NMR, ¹³C-NMR, DEPT, ¹H–¹H COSY, HSQC, HMBC). The known compounds were identified as (2S)-3′,7-dihydroxy-4′-methoxyflavan (3), (2S)-4′-hydroxy-7-methoxyflavan (4), (2S)-4′,7-dihydroxyflavan (5), 7-hydroxy-3′, 4′-methylenedioxyflavan (6), ambrettolide (7), β-sitostero1 (8), β-daucosterin (9), rutin (10), pancratistatin (11), lycorine (12), haemanthidine (13), and haemanthamine (14). In the antimicrobial assay, candidamide A (1) and candidamide B (2) displayed moderate activities against bacteria Staphylococcus aureus and Escherichia coli, and fungi Aspergillus niger, Candida albicans and Trichophyton rubrum.     

Synthesis of poly(succinimide-amide) by acid-catalyzed polycondensation of L-aspartic acid and aromatic aminocarboxylic acid

Summary The polycondensations of L-aspartic acid (1) with aromatic aminocarboxylic acid, 4-aminobenzoic acid (2a), 4-aminophenylacetic acid (2b), 4-aminomethylbenzoic acid (2c), 4-(4-aminophenyl)butyric acid (2d), and 4-aminocinnamic acid (2e) were carried out using phosphoric acid as a catalyst. The obtained copolymers consiting of the succinimide and amide units, poly(succinimide-co-amide) (3), were soluble in DMF and DMSO except for that with 2e. The thermal properties differed with varying the 2 unit in 3, i.e., the T_gs of 3a–c (99 ∼ 138°C) were higher than those of 3d (81 ∼ 1 01°C), the apparent difference in the T_m between 3a–d did not observed, and the T_d decreased in the order of 3a, 3c > 3d > 3b. Received: 24 February 1998/Revised version: 3 April 1998/Accepted: 13 April 1998     

Synthesis and Properties of Novel Antifungal Gemini Compounds Derived from <Emphasis Type="Italic">N</Emphasis>-Acetyl Diethanolamines

A series of new N-acetylated non-ionic and cationic gemini surfactants (3a–f) having dimeric structures derived from primary and tertiary amines with variably long tails (C₈–C₁₂–C₁₈) were synthesized. In addition, N-acetylated monomeric analogues 6a and 6b were prepared and their antifungal potency and surface properties were also determined. Critical micelle concentration (CMC), effectiveness of surface tension reduction (γ_CMC), surface excess concentration (Γ), and area per molecule at the interface (A) were also determined and the resulting values indicate that the cationic series is characterized by good surface-active and self-aggregation properties. For the first time, all surfactants were tested to evaluate their antifungal properties using the method for the broth macrodilution test (M27-A2, NCCLS). Four microbial strains were used to perform the study: Candida parapsilosis (ATCC 22019), C. albicans (ATCC 64548), and a wild-type strain of C. parasilosis and Saccharomyces cerevisiae (ATCC 9763). The antimicrobial activity was measured by yeast growth inhibition expressed as minimum inhibitory concentration (MIC) values. Results were compared to those obtained for their monomeric analogues and for a commercially available reference compound (Fluconazole). Gemini 3b, 3e and 3f were found to be the most potent compounds. The results show S. cerevisiae as the most sensitive strain. In contrast, the wild strain of C. parapsilosis was resistant.

Synthesis and Gas Permeability of Novel Poly(diphenylacetylenes) Having Polyethylene Glycol Moieties

4-Trimethylsilyldiphenylacetylenes with methyl group or bromine atom (Me₃SiC₆H₄C≡CC₆H₄R, R = m-CH₃, p-CH₃, m-Br, p-Br, 1a–d, respectively) were polymerized with TaCl₅/ n-Bu₄Sn to afford poly(diphenylacetylene) derivatives (2a–d). The polymers (2a–d) had high molecular weight over 5×10⁵, and gave free-standing membranes by solution casting method. Chlorination of the obtained poly[1-(3-methylphenyl)-2-(4-trimethylsilyl)phenylacetylene] was carried out by using sulfuryl chloride, and then substitution of polyethylene glycol was performed to give poly(diphenylacetylene) possessing polyethylene glycol moieties. Its carbon dioxide permeability (P_{CO 2}) and permselectivity (P_{CO 2}/P_{N 2}) were 2,970 barrers and 9.0, respectively.     

Hydrosilylation Synthesis of New Ferrocenylene Copolymers Containing Carbosilylene,Carbosiloxy and Cyclopentadienyliron Dicarbonyl Bridges

Bifunctional organometallic silicon precursor monomers and substrates FC(SiMe₂H)₂ (1) [FC = (η⁵-C₅H₄)Fe(η⁵-C₅H₄)]; FC(SiMe₂(CH₂)_xCH=CH₂)₂ [x = 0 (2), 1 (3)], [η⁵-C₅H₄-SiMe₂(CH₂)_xCH=CH₂)]Fe(CO)₂SiMe₂(CH₂)_xCH=CH₂ x = 0 (4), 1 (5) and (η⁵-C₅H₄-SiMe₂H)Fe(CO)₂SiMe₂H (6) have been used to make a series of new iron containing polymers via hydrosilylation reactions. In addition to the vinyl- and allyl-containing substrates 2, 3, 4 and 5 the organosilicon compounds [CH₂=CHSiMe₂]₂O, 1,4-(H₂C=CH-SiMe₂)₂C₆H₄ and (HC≡CH–SiMe₂)₂O were also used as substrates for the hydrosilylation reaction. The reactions between the various SiH and CH=CH₂ and C≡C functionalities were performed in the presence of Pt(0) catalyst and resulted in regioselective (β-isomer and β-(E) isomer) products as determined by NMR spectroscopy. Molecular weights of all the polymers were determined by Gel Permeation Chromatography, which revealed oligomeric materials with narrow polydispersity. Cyclic voltammetric studies of exhibited single reversible redox processes due to the Fe(II)/Fe(III) couple when present, and irreversible oxidation for the presence of any Fp Fe atom. This article is dedicated to Professor Astruc.     

N-halosuccinimide-mercaptoethanol cohalogenation of olefinic fatty methyl esters: Synthesis of β-halo thioethoxylates

Olefinic fatty methyl esters, undec-10-enoate (1), octadec-Z-9-enoate (2), methyl-12 hydroxy octadec-Z-9-enoate (3), on reaction with N-halosuccinimides (4,5), that is, N-bromosuccinimide (4) or N-chlorosuccinimide (5) and 2-mercaptoethanol (6) in benzene, gave β-bromo- or β-chlorothioethoxylates (8–13). β-Halothioethoxylates so formed were acetylated with acetyl chloride in CH₂Cl₂ to form the respective acetylated products (20–25).     

Electrochemical study of catechols in the presence of 2-thiazoline-2-thiol: application to electrochemical synthesis of new 4,5-dihydro-1,3-thiazol-2-ylsulfanyl-1,2-benzenediol derivatives

Electrochemical oxidation of catechols (1a–d) has been studied in the presence of 2-thiazoline-2-thiol (3) as a nucleophile in aqueous solution, using cyclic voltammetry and controlled potential coulometry. The results indicate that the quinones derived from catechols (1a–d), participate in Michael addition reactions with 2-thiazoline-2-thiol and via an EC mechanism pathway, convert to the corresponding catechols derivatives (4a–d and 4′d). The electrochemical synthesis of compounds (4a–d and 4′d) has been successfully performed at a carbon rod electrode and in an undivided cell with good yield and high purity. The products have been characterized by IR, ¹H NMR, ¹³C NMR and MS.     

Synthesis and characterization of poly(aryl ether ketone)s with fluorinated phenyl in the side chain

New bisphenol monomers, (4-fluorophenyl)hydroquinone (3b) and (3,4-difluoro phenyl)hydroquinone (3c), were synthesized in a two-step synthesis. Poly(aryl ether ketone)s (PAEKs) (4a–c) were derived from these fluorinated bisphenols and nonfluorinated bisphenol—phenylhydroquinone (3a) with 4,4′-diflourobenzophenone via a nucleophilic aromatic substitution polycondensation. The obtained polymers had inherent viscosities of 0.50–0.92 dL/g. Thermal analysis showed that the obtained PAEKs had excellent thermal properties, the glass transition temperatures ranged from 148 to 160 °C, and the temperatures at 5% weight loss (Td₅) were above 527 °C and the temperatures at 10% weight loss (Td₁₀) were above 544 °C in nitrogen. All the polymers showed excellent solubility and could dissolve in common organic solvents, such as DMSO, NMP, DMF, etc. So the films of them were easily cast from their solutions, which possessed good mechanical properties, with tensile strengths of 95.2–104.0 MPa, Young’s moduli of 2.68–3.06 GPa, and elongation at break of 15–32%. Furthermore, the prepared PAEKs displayed low dielectric constants (2.75–2.95 at 1 MHz) and hydrophobic character (contact angles for water: 83.9^o–98.4^o).     

Synthesis and characterization of polyimides based on isopropylidene-containing bis(ether anhydride)s

Two bis(ether anhydride)s, 4,4′-[1,4-phenylenebis(isopropylidene-1,4-phenyleneoxy)]-diphthalic anhydride (IV _a) and 4,4′-[isopropylidenebis(1,4-phenylene)dioxy]diphthalic anhydride (IV _b), were prepared in three steps starting from the nucleophilic nitrodisplacement reaction of 4-nitrophthalonitrile with α,α ′-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene (I _a) and 4,4′-isopropylidenediphenol (I _b) in N,N-dimethylformamide (DMF) in the presence of potassium carbonate. The bis(ether anhydride)s IV _a and IV _b were polymerized with various aromatic diamines to obtain two series of poly(ether amic acid)s VI _a–g and VII _a–g with inherent viscosities in the range of 0.30∼0.74 and 0.29∼1.01 dL/g, respectively. The poly(ether amic acid)s were converted to poly(ether imide)s VIII _a–g and IX _a–g by thermal cyclodehydration. Most of the poly(ether imide)s could afford flexible and tough films, and they showed high solubility in polar solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide, and m-cresol. The obtained poly(ether imide) films had tensile strengths of 45∼83 MPa, elongations-to-break of 6∼27%, and initial modulus of 0.6∼1.7 GPa. The T_gs of poly(ether imide)s VIII _a–g and IX _a–g were in the range of 194∼210 and 204∼243 °C, respectively. Thermogravimetric analysis (TG) showed that 10% weight loss temperatures of all the polymers were above 500 °C in both air and nitrogen atomspheres.     

Male-Produced Aggregation Pheromone Compounds from the Eggplant Flea Beetle (Epitrix fuscula): Identification, Synthesis, and Field Biossays

Volatiles from the eggplant flea beetle, Epitrix fuscula Crotch (Coleoptera: Chrysomelidae), feeding on host foliage, were investigated. Six male-specific compounds were detected and were identified through the use of mass spectrometry, nuclear magnetic resonance (NMR) spectrometry, chiral and achiral gas chromatography, high-performance liquid chromatography, electrophysiology (gas chromatography-electroantennography, GC–EAD), and microchemical tests. The two most abundant of the six compounds were (2E,4E,6Z)-2,4,6-nonatrienal (1) and (2E,4E,6E)-2,4,6-nonatrienal (2). The other four compounds, present in minor amounts, were identified as himachalene sesquiterpenes; two of these, 3 and 4, were hydrocarbons and two, 5 and 6, were alcohols. All four sesquiterpenes were previously encountered from male flea beetles of Aphthona spp. and Phyllotreta cruciferae. Synthetic 1 and 2 matched the natural products by GC retention times, mass spectra, and NMR spectra. Sesquiterpenes 3–6 similarly matched synthetic standards and natural samples from the previously studied species in all ways, including chirality. Both natural and synthetic 1 and 2 gave positive GC–EAD responses, as did sesquiterpenes 3, 5, and 6. Field trials were conducted with a mixture of 1 and 2, and the baited traps were significantly more attractive than control traps to both male and female E. fuscula. The E. fuscula pheromone has potential for monitoring or controlling these pests in eggplants.Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the Department of Agriculture.     

Radical polymerization of (phenylethynyl)styrenes and characterization of poly(phenylethynyl)styrenes as a thermally curable material

Summary The radical polymerizations of 2-, 3-, and 4-(phenylethynyl)styrenes (1a–c) and the copolymerizations of 1a–c (M₁) with styrene (M₂) were carried out using AIBN as the initiator in toluene at 60°C. The number-average molecular weights (M _ns) were extremely low for poly(2-phenylethynylstyrene) (2a) and poly[(phenylethynyl)styrene-co-styrene] (3a), and increased in the order of 2a, 3a << 2b, 3b < 2c, 3c. Monomer reactivity ratios were determined as r ₁= 1.80 and r ₂= 0.51 for 1a, r ₁= 1.72 and r ₂= 0.53 for 1b, and r ₁= 3.17 and r ₂= 0.24 for 1c. Polymers 2a–c and 3a–c underwent an exothermic reaction at elevated temperature to form organic solvent-insoluble polymers. Although the decomposition of 2a was observed from 200°C, 2b and 2c exhibited a high heat-resistance property in both nitrogen and air atmospheres, in particular, 2b showed no significant weight loss below 450°C. Received: 28 January 1998/Accepted: 5 March 1998