(CH3)3SiBr/AlCl3 induced cationic polymerization of 1,3-pentadiene

Cationic polymerizations of 1,3-pentadiene (PD) with AlCl₃ in n-hexane were carried out in the absence and presence of trimethylsilyl bromide (Me₃SiBr or TMSBr). Structural evidence and proton trap experiment demonstrate that in the TMSBr/AlCl₃ induced polymerization the real initiating system is the combination of AlCl₃ with HBr resulting from hydrolysis of TMSBr by adventitious water existing in the system. The conversion of the polymerization is greatly increased by adding TMSBr, but the introduction of TMSBr does not exert an effect on the formation of gel (crosslinked product). The molecular weight of the polymer prepared by TMSBr/AlCl₃ system shows a maximum in the range of [TMSBr]/[AlCl₃] = 1, and excessive TMSBr gives rise to a drop of the polymer molecular weight. Kinetic data show that AlCl₃ and TMSBr/AlCl₃ induced polymerizations have the comparable polymerization rates. Received: 12 September 1997/Revised version: 4 November 1997/Accepted: 14 November 1997     

Synthesis of polymer particles with specific lysozyme recognition sites by a molecular imprinting technique

To prepare silica beads covered with a lysozyme‐imprinted polymer layer, we polymerized acrylamide and acrylic acid or acrylamide and N,N‐dimethylaminopropylacrylamide with (NH₄)₂S₂O₈ in a phosphate buffer containing the lysozyme, surface‐modified silica beads, and crosslinkers; the result was the formation of a polymer layer with a lysozyme recognition site on the silica‐bead surface. By quantitative analysis of the supernatant of the solution containing the silica beads, we confirmed that modified silica beads, in contrast to unmodified silica beads, can selectively adsorb lysozymes. The process of binding and releasing the lysozyme to and from the modified silica beads can be repeated several times without degradation of the rebinding ability. A quartz‐crystal microbalance sensor fabricated with a molecularly imprinted polymer layer with a lysozyme recognition site was prepared. When a lysozyme aqueous solution was added to the solution in which the sensor was immersed, a high level of sensitivity and response was observed. High selectivity was also demonstrated by tests with other protein solutions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3378–3387, 2001     

Equilibrium bulk polymerization of 1,3-dioxolan

Cationic bulk polymerization of 1,3-dioxolan has been carried out in sealed ampoules using a high vacuum technique. The polymerization is initiated with triethyl oxonium hexafluorophosphate and the equilibrium between monomer and active polymer is attained within a few hours. Specific volumes of pure monomer and polymer in solution of its own monomer have been measured. Equilibrium measurements have been performed in the 40° to 141·4°C temperature range and the ceiling temperature is estimated to be 144° ± 2°C. The effect of short polymer chains on the equilibrium is discussed briefly. Values of ΔG_lc, the free energy of polymerization of one mole of pure liquid monomer to one base-mole of amorphous polymer, are computed making allowance for the non-ideal mixing. Respective values of ?17.5 ± 0.8 kJ/mol and ?47.9 ± 2.2JK^?1mol^?1 are deduced for the corresponding ΔH_lc and ΔS_lc. ΔG_lc is also computed from published data on equilibrium polymerization of 1,3-dioxolan in various solvents and the combined results for both types of polymerization yield ΔH_lc = ?16.7 ± 0.5kJ/mol and ΔS_lc = ?45.8 ± 1.5JK^?1mol^?1 for the 20° to 140°C range.     

Delocalized carbanions: synthesis and polymerization of 2,3-disubstituted-1,3-butadienes

Summary The 2,3-dimethylene-1,3-butadiene dianion (2) was prepared from 2,3-dimethyl-1,3-butadiene (1) using Lochmann's base (n-BuLi/potassium-t-butoxide in pentane). The dianion was reacted with primary halides to yield 2,3-disubstituted-1,3-butadiene monomers. These monomers were polymerized free radically with AIBN and with Ziegler/Natta coordination catalysts. The resulting polymers were examined by DSC for crystallization of the polymer backbone and alkyl side chains.     

PEO-functionalized polystyrene as polymeric support in metallocene catalysed olefin polymerisation

Summary A new catalyst system based on easily accessible cross-linked (by Diels-Alder reaction) polymeric supports, functionalized with nucleophilic polyethyleneoxide-monomethylether (PEO-M) is presented. The metallocene-MAO complex is noncovalently bonded to the support, avoiding a complicated polymer analogous metallocene synthesis. The polymerisation of propene and ethene with Me₂Si(2MeBenzInd)₂ZrCl₂ as metallocene is performed using this support. The resulting polymers have high molecular weights and melting points and narrow molecular weight distribution. Polypropene is produced with 95% isotacticity similar to that from homogeneous catalysis. The productivities of up to 8600 for polypropene and 1300 for polyethene ( kg polymer / mol Zr h bar ) are comparably high. The product beads exhibit a good morphology, which can be explained by fragmentation processes of the support due to the reversibility of the network formation. Received: 21 February 2001/Revised version: 2 November 2001/ Accepted: 6 November 2001     

Synthesis of polymers having 1,3-cyclobutanedione unit in the main chain by cycloaddition polymerization of bisketene

Summary A novel polymer having 1,3-cyclobutanedione unit in the main chain was prepared by cycloaddition polymerization of the bisketene derived from 1,4-cyclohexanedicarbonyl chloride. The polymer was soluble in MeOH, acetone, and CHCl₃. The structure of the polymer was confirmed by IR, ¹H-, and ¹³C-NMR spectroscopies compared with those of the model compounds. The polymer was found to contain anhydride bond as well as 1,3-cyclobutanedione unit in the main chain. The anhydride bond in the polymer was cleaved by MeOH under reflux condition in benzene. Received: 8 February 1999/Accepted: 16 March 1999     

Concentration effects of methylalumoxane, palladium and nickel pre-catalyst and monomer in the vinyl polymerization of norbornene

Summary The vinyl polymerization of norbornene with di-μ-chloro-bis-(6-methoxybicyclo-[2.2.1]hept-2-ene-5σ,2π)-palladium(II), Ni(acetylacetonate)₂ and Ni(2-ethylhexanoate)₂ in combination with methylalumoxane (MAO) was investigated by varying the molar MAO:metal-complex ratio, the norbornene:metal ratio and the metal concentration. The effects on the catalyst activity could be explained with a complexation equilibrium for the active homogeneous complex. Activity data in combination with polymer analyses suggest that at low, yet economical Al(MAO):metal ratios of 100 the fraction of active metal centers is less than 15%. The turnover frequency for the monomer insertion was found to reach 50 s⁻¹. Polydispersities around M_w/M_n= 2 indicate a coordination polymerization with chain transfer and a single-site character of the active centers. Received:27 February 2001/Revised version:11 November 2001/ Accepted: 20 November 2001     

Cationic copolymerization of 1,3-pentadiene with 1,3-cyclopentadiene

Copolymerizations of 1,3-pentadiene (PD) with 1,3-cyclopentadiene (CPD) initiated by aluminium trichloride were carried out in toluene. The addition of CPD in the PD polymerization system does not affect the molecular weight but greatly increases the softening point of the polymer due to the introduction of cyclic structures. The Gardner color scale of the polymer is also raised by introduction of unsaturated rings of CPD. The copolymerization gives a complete conversion but generates insoluble crosslinked gels at high CPD content due to the high crosslinking reactivity of CPD. The integral intensities of unsaturated protons from PD and CPD segments of the copolymer chain on the ¹H-NMR spectrum give a perfect correlation with the copolymer compositions. The low-conversion experiments were carried out with small amounts of CPD in order to determine the reactivity ratio in this copolymerization system (M₁ = PD and M₂ = CPD). The result of r₁ = k₁₁/k₁₂ = 0.46 demonstrates that CPD has a higher reactivity than PD toward PD growing carbocations, and hence the copolymer shows a higher CPD proportion than the corresponding comonomer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1883–1887, 1997     

Chemical anchoring of silica nanoparticles onto polyaniline chains via electro-co-polymerization of aniline and N-substituted aniline grafted on surfaces of SiO2

Chemical anchoring of silica nanoparticles onto polyaniline (PANI) chains was conducted through electro-co-polymerization of aniline and N-substituted aniline grafted on surfaces of silica nanoparticles. The grafting of N-substituted aniline on surfaces of silica nanoparticles were realized through hydrolysis of triethoxysilylmethyl N-substituted aniline (ND42) and the following condensation reaction with silanol groups on surfaces of SiO₂. Organic-inorganic interactions between PANI and SiO₂ involved in electro-co-polymerization process pushed the polymer chains apart and so facilitated the 1D growth of the polymer. Hence, the obtained hybrid film PANI/ND42-SiO₂ displayed nano-fibrous morphologies (ca. 50 nm in diameter). Consequently, PANI/ND42-SiO₂ exhibited an average specific capacitance of 380 F g⁻¹, ca. 40% higher than that of PANI/SiO₂ (276 F g⁻¹). The hybrid film also showed improved cyclic stability.     

Isocyanate-crosslinked silica aerogel monolith with low thermal conductivity and much enhanced mechanical properties: Fabrication and analysis of forming mechanisms

The applications of silica aerogels are restricted due to their intrinsic fragile property. Polymerization of di-isocyanates can be templated onto the mesoporous surface of the –NH₂ group modified silica clusters, resulting in the conformal crosslinked coating on surface of silica clusters. Aminopropyltriethoxysilane (APTES), as the silica co-precursor and amine group modification agent, is involved containing tetramethyl orthosilicate (TMOS) silica precursor, while hexamethylene diisocyanate (HDI) is incorporated as the polymer crosslinking agent. The effects of different amounts of APTES on the physicochemical properties of the resulting crosslinked aerogels are investigated. The results show that the optimized APTES/TMOS volume ratio can be determined at 0.5:1. The resulting optimal crosslinked silica aerogel possesses large BET specific surface area of 150.9 m²/g, low thermal conductivity of 0.037 W/(m·K), and the Young's modulus is as large as 18 MPa under strain of 4.2%, much higher than that in the previously published works. The polymerization reaction mechanism forming the polyurethane chains has also been proposed. In addition, the interactions between silica clusters and polymer chains are studied by molecular mechanics and molecular dynamics. The interactions are mainly dependent on non-bonding energy, and the electrostatic energy has decisive impact on the combination of silica clusters and polymer chains. The density field of C, H, N, O, and Si elements overlaps with each other, indicating that the polymer crosslinked silica aerogel maintains typical three-dimensional porous structure. The N element enriches in the region between silica clusters, further verifying the formation –CONH–(CH₂)₆–CONH- polyurethane chains, which is actually responsible for the much enhanced mechanical property.     

One-pot syntheses of water-soluble poly(oxamide)s

Two kinds of water-soluble polymers were synthesized by using the poly(oxamide) polyanion generated in situ from the reductive coupling polymerization of diisocyanates induced by SmI₂. One is a nonionic polymer bearing oligo(ethylene oxide) pendants, which was obtained by treating the polyanion with α-methyl-ω-(4-bromomethyl)phenylmethyl oligo(ethylene oxide). The other is an ion-containing polymer having sulfonate moieties in the side chains, which was prepared by the reaction of the polyanion with 1,3-propane sultone or sodium 4-(bromomethyl)-benzenesulfonate. In both cases, the corresponding polymers were provided in good yields, and their solubilities were found to be dependent on the structure as well as the substitution degree. The poly(oxamide) with oligo(ethylene oxide) exhibited good solubilities in common organic solvents and was soluble in aqueous system at high level of substitution. On the other hand, the poly(oxamide) with propane-sulfonic acid showed high solubility in both acidic and basic water but was insoluble in organic solvents, while the poly(oxamide) having benzylsulfonate was soluble only in DMF and DMSO. Received: 18 October 1996/Revised: 8 November 1996/Accepted: 15 November 1996     

Synthesis of C-unalkylated calix[4]resorcinarene from 1,3-dimethoxybenzene-formaldehyde condensation

Summary We proposed a convenient method for the synthesis of C-unalkylated calix[4]resorcinarene octamethyl ether by the HCl-catalyzed condensation of 1,3-dimethoxybenzene with paraformaldehyde in 2-ethoxyethanol. The conformation of the C-unalkylated calix[4]resorcinarene was preferentially chair-like and it changed to a boat-like by heating it in bulk and solution. Received: 26 November 2001/ Revised: 19 December 2001/ Accepted: 25 December 2001     

Synthesis of poly(methylphenylsiloxane) rich in syndiotacticity by Rh‐catalysed stereoselective cross‐dehydrocoupling polymerization of optically active 1,3‐dimethyl‐1,3‐diphenyldisiloxane derivatives

Cross‐dehydrocoupling reactions of (R)‐methyl(1‐naphthyl)phenylsilane (>99%ee) with (S)‐methyl(1‐naphthyl)phenylsilanol (>99% ee) proceeded with 82–99% retention of configuration of chiral silicon centres in the presence of various Rh‐catalysts. Cross‐dehydrocoupling polymerization of 1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediol with 1,3‐dihydro‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxane gave poly(methylphenylsiloxane) of moderate molecular weight in toluene at 60 °C in the presence of [RhCl(cod)]₂ (5.0 mol%) and triethylamine (1.0 equivalent). Assignment of the triad signals of the resulting polymer was made by ¹H NMR spectroscopy of the methyl proton (I = 0.04, H = 0.09 and S = 0.14 ppm) and ¹³C NMR spectroscopy of the ipso carbon of the phenyl group (S = 136.7, H = 136.9, and I = 137.1 ppm). Although the reaction of optically pure (S,S)‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxanediol with 1,3‐dihydro‐1,3‐dimethyl‐1,3‐diphenyl‐1,3‐disiloxane [(S,S):(S,R):(R,R)] = 84:16:0] gave a poly(methylphenylsiloxane) of rather low molecular weight, its triad tacticity was found to be rich in syndiotacticity (S:H:I = 60:32:8) by ¹³C NMR spectroscopy. © 2001 Society of Chemical Industry     

Polymerization of 1,3‐dienes containing functional groups: 8. Free‐radical polymerization of 2‐triethoxysilyl‐ 1,3‐butadiene

The presence of a bulky substituent at the 2‐position of 1,3‐butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free‐radical polymerization of 2‐triethoxysilyl‐1,3‐butadiene ( 1 ) was carried out under various conditions, and its polymerization behavior was compared with that of 2‐triethoxymethyl‐ and other silyl‐substituted butadienes. A sticky polymer of high 1,4‐structure ( ) was obtained in moderate yield by 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerization. A smaller amount of Diels–Alder dimer was formed compared with the case of other silyl‐substituted butadienes. The rate of polymerization (R_p) was found to be R_p = k[AIBN]^0.5[ 1 ]^1.2, and the overall activation energy for polymerization was determined to be 117 kJ mol^?1. The monomer reactivity ratios in copolymerization with styrene were r ₁ = 2.65 and r_st = 0.26. The glass transition temperature of the polymer of 1 was found to be ?78 °C. Free‐radical polymerization of 1 proceeded smoothly to give the corresponding 1,4‐polydiene. The 1,4‐E content of the polymer was less compared with that of poly(2‐triethoxymethyl‐1,3‐butadiene) and poly(2‐triisopropoxysilyl‐1,3‐butadiene) prepared under similar conditions. Copyright © 2010 Society of Chemical Industry     

Poly(1,2‐diaminobenzene) and poly(1,3‐diaminobenzene): Synthesis,characterization, and properties

Poly(1,2‐diaminobenzene) (1,2‐DAB) and poly(1,3‐diaminobenzene) (1,3‐DAB) have been synthesized by using ammonium persulfate as oxidizing agent in the presence and in the absence of the following metal ion salts: CuCl₂, NiCl₂, and CoCl₂ with different HCl concentrations. The products showed a different content of the metal ion depending on the HCl concentration. The polymers were characterized by Fourier transform infrared (FTIR), ultraviolet‐visible (UV‐Vis) spectroscopy, thermal analysis, and electrical conductivity. The polymerization yield depended on the presence of metal ions that can react as oxidizing reagents and/or catalysts. The polymerization mechanism depended on the position of the substituent. For poly(1,2‐DAB) a ladder‐type structure was obtained, and for poly(1,3‐DAB) one similar to that of polyaniline. The thermal stability increased as the metal ion content in the polymer matrix increased. The electrical conductivity of the polymer did not depend on the metal ion content in the polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2564–2572, 2002     

Effects of trisobutylaluminium on styrene polymerization with Ni(acac)2 /MAO/SiO2 catalyst system activated by methylaluminoxane

Summary Styrene polymerization with Ni(acac)₂/MAO/SiO₂ catalytic system was carried out in the presence of methylaluminoxane (MAO), triisobutylaluminum (TIBA) or MAO and TIBA mixture as activators. The catalytic system activated only by TIBA produced polymer with 53% of isotacticity. When the catalytic system was activated by a mixture of MAO and TIBA the polymer isotacticity increases as MAO concentration increases. In this case, the maximum of isotacticity was 59%. The polymer has presented lower molecular weight than the polymer obtained by MAO as activators and the polymer microstructure was not explained by Markov first-order model. In addition, ¹³C NMR spectra of the polymers obtained after extraction with MEK, have indicated that there are two active sites in this catalytic system. Received: 28 November 2001 / Revised version: 24 May 2002 / Accepted: 29 May 2002     

Dynamic-mechanical thermal analysis of aramid-silica hybrid composites prepared in a sol-gel process

Several types of nonbonded and chemically bonded composites of silica with linear and linear-nonlinear aramid polymers were prepared using the sol-gel process. The linear polyamide chains were synthesized by the reaction of a mixture of m- and p-phenylene diamines and terephthaloyl chloride in dimethyl acetamide. The nonlinear chains were prepared using 1,3,5-benzenetricarbonylchloride along with tereph-thaloyl chloride, thereby significantly increasing the average functionality of the monomers. These increased functionality chains were then endcapped with aminophenyl-trimethoxysilane. Silica networks chemically bonded to the polyamide chains were produced by the addition of tetramethoxysilane to the aramid solution and its subsequent hydrolysis and condensation. The films cast from these solutions were yellow, and those containing up to 25 wt % silica were also transparent. Dynamic-mechanical thermal analysis was carried out to characterize interfacial bonding and interactions, in particular through the use of values of the glass transition temperatures T_g of the polymers. The presence of the silica caused increases in T_g, with the increases being largest for the composites in which there was strong interfacial bonding between the polymer chains and the ceramic silica phase. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1345–1352, 1997     

Bulk functional oligomerization of ɛ-caprolactone in a mini extruder

Summary ɛ-caprolactone has been polymerized in bulk in a mini-extruder with Al(OiPr)₃ as initiator and benzyl alcohol as transfer agent. Polymer chains have been characterized by ¹H NMR, SEC and Maldi-Tof mass spectroscopy in order to investigate the potentialities of this process in terms of macromolecular engineering. Low temperatures around 75°C are enough to perform oligomerization at high conversion with a mean residence time less than 2 minutes. All the polymer chains are actually functionalized by the chemical group issued from the transfer agent. Molecular weight distribution depends on the temperature as well as on the residence time. Received: 3 October 2001/Revised version: 18 February 2002/ Accepted: 7 M?rz 2002     

Organic–inorganic composite materials from acrylonitrile–butadiene–styrene copolymers (ABS) and silica through an in situ sol‐gel process

Nonbonded and chemically bonded organic–inorganic composite materials, ABS/SiO₂ and ABS Si(OCH₃)₃/SiO₂, were prepared by the sol‐gel processing of tetraethoxysilane (TEOS) in the presence of ABS and trimethoxysilyl functionalized ABS, ABS Si(OCH₃)₃, under the catalization of NH₄F. The ABS Si(OCH₃)₃ was obtained by oxidizing the cyano group in ABS with hydrogen peroxide, then subsequently underwent ring‐opening reaction with 3‐glycidoxypropyltrimethoxysilane (GPTS). The ABS Si(OCH₃)₃/TEOS sol‐gel liquid solution system, in which the ABS chains formed the covalent bonds with silica network and helped fix the polymer chains in the silica network, had a shorter gelation time than that of the ABS/TEOS system, which linked ABS chains to the silica network only by hydrogen bonding the cyano groups in ABS to the silanol groups. The morphology and properties of composite were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), tensile tests, and thermogravimetry. It was found that the composite prepared from ABS Si(OCH₃)₃ had higher tensile strength, glass transition point (T_g), thermal stability, and more homogeneous morphology because of the existence of the covalent bond between ABS chains and silica network that increased the compatibility between the organic and inorganic phases. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 275–283, 2000     

Silica concentration dependence of the kinetics of polydimethylsiloxane adsorption on aggregates

Summary   The kinetics of adsorption of pure polydimethylsiloxane or of bimodal mixtures, onto silica aggregates, was observed from the melt as a function both of polymer weight fraction (2.5 to 20 g/g) and of the specific area (50, 150 and 300 m²/g). Attention was focused on filled polymers wherein silica aggregates are connected to one another by adsorbed chains to form a network. Results were analysed according to a molecular approach. All observed kinetics curves were found to obey a property of superposition by using a suitable reduced time variable defined as :