Thermal behaviour and adhesive properties of some cyanoacrylate adhesives with increased heat resistance

Cured adhesive layers produced from ethyl-(ECA), allyl-(ACA), and allyloxyethyl-(AOECA) 2-cyanoacrylates were studied by means of thermogravimetry and differential scanning calorimetry. Polymer films of ECA-based adhesive compositions comprising various amounts and types of 2-cyano-2,4-pentadienoic acid (CPDA) esters were also examined. The influence of the modifier type, as well as the chemical structure of the cyanoacrylates used, was followed upon the glass transition temperatures (T_g) and the rates of thermal degradation of the corresponding polymers. In the case of cured adhesive mixtures containing unsaturated CPDA esters and when poly(ACA) and poly(AOECA) were studied, a significant increase of their heat resistance was established, as compared with poly(ECA). This fact was explained with the formation of three-dimensional structure of the polymer film due to crosslinking reactions. A different course and character of these reactions were found comparing the thermal behavior of poly(ACA) and cured compositions containing unsaturated CPDA esters. A good agreement was found between data from the thermal analyses and the tensile shear and impact strength tests. It was shown that the modification of ECA with unsaturated CPDA esters is a possible way of increasing the heat resistance of the basic adhesive. © 1993 John Wiley & Sons, Inc.     

Dienes and diamondoids: poly(2-[1-adamantyl]-1,3-butadiene) and random copolymers with isoprene via redox-emulsion polymerization and their hydrogenation

A novel route to adamantane substituted diene copolymers is demonstrated using emulsion polymerization, with an improved monomer synthesis. Heterogenous dehydration of 2-(1-adamantyl)-3-buten-2-ol using Amberlyst®-15 cationic exchange resin at ambient temperature gave 2-(1-adamantyl)-1,3-butadiene ( 1 ) in excellent yield and presents an attractive alternative monomer synthesis route. Emulsion polymerization of 1 and mixtures of 1 and isoprene was carried out at room temperature using redox pair, hydroperoxide initiator. All poly( 1 ) and poly( 1 -ran-isoprene) samples were soluble in common organic solvents and exhibited high 1,4-microstructure. A continuous increase in glass transition temperature from −63 to 172°C was observed by increasing the ratio of 1 in the comonomer feed of poly( 1 -ran-isoprene), and T_g values were in good agreement with the Fox equation. After complete hydrogenation to poly(1-vinyladamantane-alt-ethylene-ran-propylene-alt-ethylene), a continuous increase in T_g was observed from −55 to 152°C. The high solubility and improved access to 2-(1-adamantyl)-1,3-butadiene opens the door to exploration of diene polymers with enhanced high temperature properties.     

Alkaline hydrolysis of homopolymers and copolymers of 2-hydroxypropyl methacrylate

Homopolymers of 2-hydroxypropyl methacrylate (HPMA) and copolymers with acrylic acid (AA) were prepared in 1,4-dioxane. The reactivity ratios were determined to be r_AA = 0.27 ± 0.04 and r_HPMA = 2.2 ± 0.2. The alkaline hydrolysis by sodium hydroxide of the HPMA monomer and polymers showed that while the HPMA monomer hydrolyzed readily as expected for a low-molecular-weight carboxylic ester the HPMA homopolymer and water-soluble sodium acrylate (NaA) copolymers were extremely resistant to alkaline hydrolysis. The saponification reaction followed a second-order rate equation, being first order with respect to both HPMA and hydroxide ion concentration. The Arrhenius parameters, activation energy E and frequency factor A, for the alkaline hydrolysis of HPMA monomer in water were found to be E = 10.3 Kcal/mol and A = 1.5 × 10⁸ L/mol min, and those for the NaA–HPMA copolymers in water were found to be E = 24 kcal/mol and A = 4 × 10¹² L/mol min. The NaA–HPMA copolymers had a limiting extent of hydrolysis, ranging from 9–90% ester conversion. A sharp rate decrease at low conversion was noted during the HPMA homopolymer hydrolysis in 58/42 dimethyl sulfoxide/water, allowing the calculation of two distinct reaction rates. © 1992 John Wiley & Sons, Inc.     

Organoselenium-mediated cyclization of hydroxyolefinic fatty acids and m-CPBA oxidation of selenium-containing 1,4-epoxy acids

Chlorophenylselenenylation methodology is shown to cause cyclization of naturally occurring β- and γ-hydroxyolefinic acids. The phenylseleno-substituted 1,4-epoxides (tetrahydrofurans) thus obtained are oxidized by m-chloroperbenzoic acid (m-CPBA). Reaction of phenylselenenyl chloride with methyl 12-hydroxyoctadec-cis-9-enoate (methyl ricinoleate) gave methyl 9,12-epoxy-10-phenylselenenyloctadecanoate in useful yields. A similar reaction of phenylselenenyl chloride with methyl 9-hydroxyoctadec-cis-12-enoate afforded a quantitative yield of methyl 9,12-epoxy-13-phenylselenenyloctadecanoate. Oxidation of selenium-containing 1,4-epoxy esters by m-chloroperbenzoic acid (1 equivalent) yielded the respective olefinic 1,4-epoxy esters, while 5 equivalent m-CPBA afforded the corresponding oxirane esters of epoxytetrahydrofurans in high yields. The structure of the individual reaction products have been established from analytical and spectral data and corroborated by a study of their mass spectra.     

Microwave induced synthesis of thieno[2,3-b]quinoline-2-carboxylic acids and alkyl esters and their antibacterial activity

A series of thieno[2,3-b]quinoline-2-carboxylic acids and alkyl esters, (3a–i) have been synthesized by the condensation of 2-chloro-3-formyl quinolines (1a–c) with thioglycolic acid/alkyl esters under microwave irradiation using anhydrous potassium carbonate. These compounds were characterized by elemental analysis, IR, ¹H NMR, and mass spectral studies. Their antibacterial activity was also evaluated.     

n-Hexyl Laurate and Fourteen Related Fatty Acid Esters: New Secretory Compounds from the Julid Millipede, Anaulaciulus sp.

A total of fifteen saturated fatty acid esters were newly identified from the secretions of an unidentified Anaulaciulus sp. (Julida: Julidae). The fatty acid components of the esters were composed of normal chain acids (from C₁₀ to C₁₄) and of branched chain acids (from iso-C₁₂ to iso-C₁₅ and anteiso-C₁₅). The alcohol moieties were all composed of normal chain alcohols varying from n-butanol to n-octanol. The most abundant component found in the total esters was n-hexyl laurate (64.7%). Novel compounds identified from the millipede secretion extracts include six branched iso- and anteiso-fatty esters, an odd-numbered C₁₁-fatty acid ester, a C₁₃-fatty acid ester, and a C₇-alcohol ester, all of which were previously undescribed natural products. In addition, a characteristic mixture of benzoquinones, such as 2-methyl-1,4-benzoquinone, 2-methoxy-3-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, 2-methoxy-6-methyl-1,4-benzoquinone, and 2,3-dimethoxy-5-methyl-1,4-benzoquinone were identified from the secretions, together with trace amounts of 1,4-benzoquinone.     

DSC study of thermal decomposition of partially ozonized diene rubbers

The thermal decompositions of partially ozonized 1,4-cis-polybutadiene (E-BR), 1,4-cis-polyisoprene (E-IR), 1,4-trans-polyisoprene (Z-IR), 1,4-trans-polychloroprene (Z-PCh), and of polybutadiene elastomer (BR) (microstructure: 1,4-cis, 47%; 1,4-trans, 42%; 1,2, 11%) were studied. The respective thermograms were described by the presence of an intense and relatively broad exothermic peak in the 60–200°C range, which is the result of thermolysis of functional groups of the peroxide type. The measured values of the enthalpy of the reaction, normalized with respect to the amount of reacted ozone (kJ/mol O₃), were as follows: 337 (E-BR), 260, (BR), 197 (E-IR), 180 (Z-IR), and 239 (Z-PCh). Values of the activation energy and reaction order were also determined: 122.6, 118.5, 108, 113, 101.5 and 1.0, 0.96, 1.04, 1.08, and 1.25, respectively. The enthalpy values, obtained by means of differential scanning calorimetry, should be used for quantitative determination of ozonides from polydienes and polyisoprenes. © 1996 John Wiley & Sons, Inc.     

A novel perfluorocyclobutyl aryl ether-based graft copolymer via 2-methyl-1,4-bistrifluorovinyloxybenzene and styrene

A series of novel perfluorocyclobutyl aryl ether-containing graft copolymers with polystyrene side chains were synthesized by the combination of thermal step-growth [2π + 2π] cycloaddition polymerization of aryl bistrifluorovinyl ether monomer and atom transfer radical polymerization (ATRP) of styrene. We first synthesized a new aryl bistrifluorovinyl ether monomer of 2-methyl-1,4-bistrifluorovinyloxybenzene in two steps using commercially available 2-methylhydroquinone as starting material and the corresponding perfluorocyclobutyl aryl ether-based homopolymer with methoxyl end groups was prepared through the homopolymerization of this monomer in diphenyl ether. Next, the pendant methyls of this fluoropolymer were mono-brominated by N-bromosuccinimide and benzoyl peroxide so as to be converted to ATRP initiation groups. The targeted poly(2-methyl-1,4-bistrifluorovinyloxybenzene)-g-polystyrene with relatively narrow molecular weight distributions (M_w/M_n ≤ 1.38) was obtained by the combination of bulk ATRP of styrene at 110 °C using CuBr/bpy as catalytic system and the grafting-from strategy. These fluorine-containing graft copolymers show excellent solubility in common organic solvents.     

Possible function of ecdysteroid-22-O-acyltransferase in the larval gut of tobacco budworm,Heliothis virescens

In the larval gut of the tobacco budworm,Heliothis virescens, most ingested ecdysteroids are transformed to ecdysteroid-22-acyl esters by a novel enzyme, ecdysteroid-22-O-acyltransferase. This conversion is different from the normal metabolic pathway in which the compounds are usually transformed to more water-soluble products. Most ecdysteroid-22-O-acyltransferase activity was found in the midgut epithelial-cell membrane and was active only during feeding stages. The activity decreased as the larvae became committed to pupation, and it was not enhanced by feeding ecdysteroids to the fifth-instar larvae. Our preliminary results showed that the esterification was very specific to 22-OH in ecdysteroids. We suggest that detoxification is the major function of ecdysteroid-22-O-acyltransferase.     

Phase equilibria in SBR/polybutadiene elastomer blends: Application of Flory–Huggins theory

Blends of anionically-polymerized polybutadiene (BR) and styrene–butadiene copolymer (SBR) must be treated as mixtures of terpolymers and tetrapolymers, due to the presence of three different BR isomers: cis-1,4, trans-1,4, and vinyl-1,2. Moreover, in the absence of specific interactions or chemical reactions that strongly influence miscibility, structural characteristics of the component polymers, such as BR isomer content, SBR styrene content, monomer sequence distribution, molecular weight, and molecular weight distribution, are expected to have an increased role in determining the blend miscibility characteristics. Small angle neutron scattering (SANS) studies of SBR/BR blends have resulted in the computation of the monomer–monomer segmental interaction energetics via a Flory–Huggins treatment. This allows quantitative prediction of miscibility behavior as a function of polymer structure. We have used the Flory–Huggins chi parameters, describing the styrene/cis-1,4, styrene/trans-1,4, and cis-1,4/trans-1,4 segmental interactions, to identify certain blend combinations expected to exhibit phase transitions in an experimentally accessible temperature range. The appropriate polymers were synthesized, solution blended, and the blends analyzed via optical microscopy and thermal analysis. Our results show that the blend behavior, observed experimentally, is consistent with the calculated cloud point curves. © 1994 John Wiley & Sons, Inc.     

Esterification of ethylenediaminetetraacetic acid

The esterification of ethylenediaminetetraacetic acid (EDTA) in a hot acidic medium gives rise to impure products. The impurities have been identified and shown to be esters of various acids: nitrilotriacetic acid; iminodiacetic acid; piperazine-1,4-diacetic acid; N-methylethylenediaminetriacetic acid; N,N- and N,N′-dimethylethylenediaminediacetic acids and 2-ketopiperazine-1,4-diacetic acid. The reactions for the formation of these impurities are discussed and a method for the preparation of pure esters of EDTA is described. Details of some crystalline derivatives, ¹H-n.m.r. and infrared spectra of a series of esters of EDTA are presented. The determination of the molecular weights of the esters by saponification is discussed.     

Facile synthesis of some novel 4-{3-aryl-3, 4-dihydro-2H-benzo[b][1,4] thiazin-2-yl}-2H-chromen-2-one derivatives

A protocol for chemoselective one pot synthesis of 4-{3-aryl-3, 4-dihydro-2H-benzo[b][1,4]thiazin-2-yl}-2H-chromen-2-ones 4 and 4-{3-aryl-3, 4-dihydro-2H-benzo[b][1,4]thiazin-2-yl}-2H-chromen-2-ones 6 under refluxing conditions has been developed. Starting from 4-bromomethylcoumarin and Schiff base, which is derived from o-aminothiophenol and substituted aromatic aldehydes, the intermediate sulfide spontaneously underwent intramolecular carbanion addition across the azomethine carbon.     

Synthesis and characterization of copolymers with alternating 1,4-bis(5'-acetyl-2'-thienyl)benzene or 1,3-bis(5'-acetyl-2'-thienyl)benzene chromophore and disiloxane units

Summary Activated (Ph₃P)₃RuH₂CO (Ru) catalyzed copolymerization of 1,4-bis(5'-acetyl-2'-thienyl)benzene (I) and 1,3-divinyltetramethyldisiloxane (II) yields alt-copoly[3,3,5,5-tetramethyl-4-oxa-3,5-disila-1,7-heptanylene/2',2"-diacetyl-5',5"-(1,4-benzene)-3',3"-bis (thiophenylene)] (III). On the other hand, Ru catalyzed copolymerization of 1,3-bis(5'-acetyl-2'-thienyl)benzene (IV) and II fails. Nevertheless, Ru catalyzed reaction of IV with excess vinylpentamethyldisiloxane (V) yields 1,3-bis(4'-pentamethyldisiloxy-ethyl-5'-acetyl-2'-thienyl)benzene (VI). VI undergoes acid catalyzed siloxane equilibration polymerization to give alt-copoly[3,3,5,5-tetramethyl-4-oxa-3,5-disila-1,7-heptanylene/2',2"-diacetyl-5',5"-(1,3-benzene)-3',3"-bis(thiophenylene)] (VII) and hexamethyldisiloxane. Copolymers III and VII have been characterized. Received: 26 July 1999/Revised version: 12 October 1999/Accepted: 12 October 1999     

Modelling and parameter estimation of trans-β-farnesene coordination polymerization

trans-β-Farnesene is a bio-derived terpene monomer that can polymerize, generating polymers with properties that can be similar to the properties of conventional petroleum-derived polymers. For this reason, in the present study, several coordination polymerizations of trans-β-farnesene are carried out using the Ziegler–Natta catalyst system composed by neodymium versatate (${\mathrm{NdV}}_3$), diisobutylaluminum hidride (DIBAH), and dimethyldichlorosilane (DMDCS) in order to evaluate the influence of key operation variables on the control of average molar masses and monomer conversion. A phenomenological model is proposed to describe the coordination polymerization of trans-β-farnesene, and the kinetic parameters required to simulate the reactions are estimated. The initial concentration of DIBAH used as a chain transfer agent (CTA) is calculated by a data reconciliation procedure since this very active compound can participate in undesired side reactions. It is shown that the initial monomer, DIBAH, and ${\mathrm{NdV}}_3$ concentrations exert strong influences on the monomer conversion and average molar masses of (poly)farnese while the temperature effect is not so pronounced. The proposed kinetic mechanism was able to predict well the experimental data collected during the reactions, with the successful reconciliation of CTA concentrations and estimation of model parameters.     

Enzymatic synthesis of monosaccharide fatty acid esters and their comparison with conventional products

5-O-Acyl-1,2-O-isopropylidene-D-xylofuranose and 6-O-acyl1,2∶3,4-di-O-isopropylidene-D-galactopyranose were enzymatically prepared from the corresponding monosaccharide acetals and commercial (crude) fatty acid mixtures. Subsequent acid-catalyzed hydrolysis of the isopropylidene group(s) gave monosaccharide esters with overall yields of 59–88%, where the monoester content was at least 80% (galactose oleate) and typically 90% for the other preparations. In contrast to sugar fatty acid esters prepared by conventional, high-temperature (trans)esterification, the enzymatically obtained monosaccharide esters contained no appreciable quantities of undersirable side products, and the only contaminants were monosaccharides and fatty acids.     

Zinc‐based catalyst for the ring‐opening polymerization of cyclic esters

A zinc‐based catalyst zinc bis[bis(trimethylsilyl)amide] was used for the polymerization of cyclic esters including L ‐lactide (L ‐LA) and 2‐methyl‐2‐carboxyl‐propylene carbonate (MBC). The polymerization of L ‐lactide in THF could be carried out successfully under mild conditions in very short time by using the zinc catalyst and alcohols as the initiators. Kinetic study in solution polymerization prooved the polymerization has high monomer conversion degree close to 100% and the molecular weight of the resulting polyester has linear increase with the increase of [M]₀ /[I] (molar ratio of monomer to initiator). Sequential polymerization of L ‐LA and MBC in THF also showed high MBC conversion of 94% with a narrow molecualr weight maintained, indicating a living nature of this polymerization. The zinc catalyst system has also been used for the L ‐LA bulk polymerization with a high monomer conversion. ¹³C NMR indicated the polymer possesses high regioregularity and the minor regioirregular component was owing to the D ‐LA in the monomer inserted into the polymer mainchain during the transesterifcation. Interaction between monomer and zinc catalyst has been found to be a key factor to sustain a homogenous solution during the initiating procedure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

One-pot synthesis of poly(methacrylic acid)-b-poly(2,2,2-trifluoroethyl methacrylate) diblock copolymers via RAFT polymerization

In this work, the reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to synthesize the amphiphilic diblock copolymers of poly(methacrylic acid)-b-poly(2,2,2-trifluoroethyl methacrylate) (PMAA-b-PTFEMA) via one-pot two-step reaction protocol. The controlled radical polymerization of MAA monomer was first carried out in pure water by using 4-cyanopentanoic acid dithiobenzoate (CADB) as chain transfer agent. Subsequently, the as-synthesized PMAA homopolymers with dithiobenzoate end-groups were employed as macro-CTA and chain-extended in situ with the hydrophobic TFEMA monomer. The reactions were carried out in 1,4-dioxane/water medium. Both the polymerization of PMAA and PTFEMA blocks showed the well controllability on the molecular weighs and distributions. It was found that the amphiphilic diblock copolymers formed the stable spherical particles via the polymerization-induced self-assembly. Meanwhile, the effect of various parameters, such as the concentration ratio of TFEMA monomer over PMAA macro-CTA, the solvent condition (different ratio of 1,4-dixane/water), and the pH, on the RAFT polymerization of TFEMA monomer were investigated in detail. Their kinetic results suggested that the propagation of TFEMA monomer on the macro-CTA was performed at the particle/water interfaces. The concentration of chain transfer agents at the interfaces determined the polymerization rate. Finally, the stability of the fluorinated polymer dispersions was also evaluated in this work.     

The determination of the addition variation and geometrical isomerism of a polybutadiene as a function of molecular weight by preparative gel permeation chromatography and infrared analysis

The addition variation, 1,2 and 1,4 units, and the geometrical isomerism, 1,4-cis and 1,4-trans units, of a fractionated polybutadiene were determined as a function of molecular weight using preparative gel permeation chromatography followed by infrared analysis of the fractions. Both the addition variation and geometrical isomerism remained essentially constant across the molecular weight distribution.     

2-alkenyl-4,4-dimethyloxazolines as derivatives for the structural elucidation of iosmeric unsaturated fatty acids

Several types of unsaturated fatty acid methyl esters were converted into 4,4-dimethyloxazoline (DMOX) derivatives and analyzed by mass spectrometry to further evaluate the feasibility of using this derivative for locating the positions of double bonds in isomeric fatty acids. Five isomeric 20-carbon tetraenoic acids were analyzed in which the fourcis double bonds were systematically moved from the 4,7,10,13- to the 8,11,14,17-positions. It was possible to locate the positions of all four double bonds in the 7,10,13,16- and 8,11,14,17-isomers by appropriate ions differing by 12 atomic mass units. In a similar way the three terminal double bonds in the 4,7,10,13-, 5,8,11,14- and 6,9,12,15-isomers could be assigned. Odd-numbered ions atm/z 139, 153 and 167 which are accompanied by an even mass ion at 138, 152 and 166, respectively, are diagnostic for DMOX derivatives of acids with their first double bond, respectively, at positions 4, 5 and 6. It was thus possible to assign the location of all four double bonds in these three isomers. A comparison of the spectra of the DMOX derivatives of 17,17,18,18-d ₄ vs. 9,10,12,13-d ₄ linoleic acid suggests that double bonds preferentially migrate toward the polar end of the molecule prior to fragmentation. The merit of using DMOX derivatives to locate double-bond positions in mono- and dicarboxylic acids, produced during β-oxidation of polyunsaturated fatty acids, was evaluated. The spectra of 3-cis- and 4-cis-decenoic acids differ as do the spectra of 8-carbon dicarboxylic acids with their double bonds at positions 3 and 4.     

Gas transport in poly(vinyl-p-isopropylbenzoate): Comparison and correlation with some other poly(vinyl esters)

Gas permeability in poly(vinyl-p-isopropylbenzoate) (PVp-i-PrB) was determined by a timelag method. The transport properties were discussed from comparison with the permeability data of other poly(vinyl esters), which were studied previously. All these polymers are structurally related, and the size of a side group or the position of its substituent was changed systematically. The isopropyl group of PVp-i-PrB is attached at the para position of a phenyl ring and is the largest in size. As a result gas diffusivity and therefore permeability were increased. The effect of the substituent on gas diffusivity was explained as it increases the interchain and intrachain distances. The discussion was supported from the comparison of the density data between PVp-i-PrB and other poly(vinyl esters). The diffusion coefficients of six glassy poly(vinyl esters) were correlated at their T_g and good correlations were shown to the free volume and its fraction. On the other hand, gas solubility was little affected by the change of an alkyl group on a phenyl ring. The solubility data of PVp-i-PrB and poly(vinyl benzoate) were shown to be clearly correlated with the critical properties of the penetrants. © 1995 John Wiley & Sons, Inc.