Two-component copolymer networks. Synthesis of polystyrene/poly(dimethylsiloxane) copolymer network and its swelling behavior in mixed solvents

A two-component copolymer network comprising polystyrene (PS) and poly(dimethylsiloxane) (PDMS) as copolymer components was prepared by cross-linking PS with telechelic PDMS. In the first stage of the cross-linking reaction, PS having 5–6 mol -% of sodium acrylate units along the main chain was ionically coupled with bifunctional PDMS having 1-methylpyrrolidinium salt groups on both chain ends, and then the ionic coupling was converted to covalent bonds at 100°C by ring-opening of the 1-methylpyrrolidinium salt upon nucleophilic attack of the carboxylate counter anion. The resulting PS/PDMS networks were subjected to investigation of swelling behavior in three kinds of mixed solvents which were chosen so as to contrast with one another in respect of solubility of the component polymers. Three different types of swelling behavior were obtained which regard to the solvent composition dependence.     

Tailored synthesis of branched polymers with poly(tetrahydrofuran) having an azetidinium salt end group

Monofunctional poly(tetrahydrofuran), (poly(THF)), having a 1-(diphenylmethyl)azetidinium end group ( 1 ) was prepared and subjected to an ion-coupling reaction with various mono- and plurifunctional carboxylates ( 2a–j ). Multiarmed polymers having 2, 3, 4 and 6 arms were obtained in almost pure form by repeating a simple precipitation of a THF solution of 1 into an ice-cooled aqueous solution containing an excess amount of the relevant plurifunctional carboxylates ( 2 c – g ) as sodium salts. Another model-branched polymacromonomer was obtained in high yield through the macromolecular ion-coupling reaction of 1 with poly(sodium acrylate) ( 2 h ) of DP = 22. Moreover, the ion-coupling reaction of 1 with sodium (L )-tartarate ( 2 i ) or sodium 2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylate ( 2j ) allowed one to introduce two hydroxyl groups at the center of a linear poly(THF) segment.     

Preparation of poly(methylfluorosiloxanes) by living anionic polymerization initiated with dilithium salt of N,N ′‐bis(diphenylhydroxysilyl)tetramethylcyclo‐disilazane

A bifunctional living poly(methyltrifluoropropylsiloxane) PMTFS, was synthesized through the anionic ring‐opening polymerization of trans‐1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl) cyclotrisiloxane (trans‐F₃) (3) with an initiator of dilithium salt (2) of N,N ′‐bis(diphenylhydroxysilyl)tetramethylcyclodisilazane (1) in ethyl acetate. The subsequent end‐capping reaction of the bifunctional living PMTFS with dimethylvinylchlorosilane (4) provided the uniform size PMTFS having vinylsilane group at both chain ends.     

Synthesis,characterization and photoreaction of side-chain liquid-crystalline polymers comprising cinnamoyl biphenyl mesogen

Liquid-crystalline (meth)acrylate monomers and polymers having mesogenic groups based on 4-alkyloxy-4′-cinnamoylbiphenyl (m = 2, 6) were synthesized. The methacrylate monomers 4c, d were polymerized by free radical polymerization. Under the same conditions, the acrylate monomers 4a, b gave unidentified polymers in very low yield. To synthesize the acrylate polymer, the acrylate monomer having 4-alkyloxy-4′-hydroxybiphenyl (m = 2, 6) was polymerized followed by the esterification of the hydroxy group using cinnamoyl chloride. All synthesized polymers having mesogenic moieties showed liquid-crystalline phases in the high temperature range between 140°C and 245°C. The difference of aggregation of the cinnamoyl biphenyl mesogen among the polymers was studied by UV-VIS spectroscopy at various temperatures. The photoreaction was performed in both solution and thin film. The [2+2] cycloaddition reaction preferentially occurred in the thin film although both [2+2] cycloaddition and photo-Fries reactions could occur in the solution.     

Ion exchange and ring-opening reactions of telechelic poly(tetrahydrofuran)s containing terminal cyclic quaternary ammonium salts

Anion exchange and ring-opening reactions of cyclic quaternary ammonium salt end groups of poly(tetrahydrofuran) [poly(THF)] were studied. The counter anion exchange reaction of the quaternary ammonium triflate to the sulfonate or to the carboxylate, was found to take place by precipitation of the starting poly(THF) prepolymer from an aqueous solution containing the corresponding sodium salt. The azetidinium salt 1 was found to undergo ring opening reaction with its carboxylate counter ion at ambient temperature, whereas the pyrrolidinium salt 2 needs heating up to 100°C. The ring-opening reactivities of the cyclic ammonium salts of poly(THF) chain ends were compared with those of model systems.     

Synthesis of novel functional styrene monomers having trimethylsilyl and hydroxyalkyl groups by the reaction between 4-vinylbenzyllithium derivatives and oxiranes

New synthetic routes for styrene derivatives having both trimethylsilyl and hydroxyalkyl groups were investigated. Reactions between oxirane ( 5a ) and chemical species present in an equilibrium system resulting from 4-(trimethylsilylmethyl)styrene ( 1s ) and lithium diisopropylamide ( 2 ) in tetrahydrofuran give an addition product ( 8a ) between 2 and 5a preferentially. By using alkyl-substituted oxiranes such as ethyloxirane ( 5c ) and tert-butyloxirane ( 5e ), a 1 : 1 addition reaction of 1s with the oxiranes takes place predominantly to form 1-alkyl-3-trimethylsilyl-3-p-vinyl-phenyl-1-propanol ( 8 ) homologues. From results of studies on the reaction between 2 and several oxiranes, it was concluded that the selective formation of 8 homologues was attained by suppression of reactions between oxirane and 2 owing to steric hindrance between alkyl substituents of oxirane and isopropyl groups of 2 . The reactivity of 8 in polymerization reaction was also estimated on the basis of spectroscopic measurements. 8 was found to have a reactivity similar to that of 4-(trimethylsilylmethyl)styrene ( 1s ).     

Lithium amide catalyzed anionic polyaddition of 1,4-divinylbenzene with N,N′-diethylethylenediamine

Lithium amide catalyzed anionic polyaddition of N,N′-diethylethylenediamine ( 6 ) to 1,4-divinylbenzene ( 9 ) was carried out to obtain a new type of polyamine possessing a polymerizable vinyl group at the chain end, a so-called “macromer”. Analyses of the reaction and of the resulting polyamine by means of ¹³C NMR and GPC revealed that this polyaddition reaction is a typical equilibrium reaction which is not accompanied with any side reactions, except with a possible cyclization reaction. The equilibrium constants K and their temperature dependence were determined and compared with those of model reactions. The rate constants k₁ of the first step reaction and k₂ of the second step were also determined independently.     

Synthesis of a diphenylethylene derivative carrying aromatic tertiary amine groups and its use in chain end functionalization of alkyllithium-initiated polymerizations

1,1-Bis[(4-dimethylamino)phenyl]ethylene was successfully synthesized through the ‘Wittigtype’ reaction of 4,4′-bis(dimethylamino)benzophenone with the ‘Tebbe’ reagent. The methylenation yields were over 80 wt.-% on the basis of the initial amount of benzophenone derivative used. Terminally functionalized polymers having aromatic tertiary amine groups at one end or at both ends were prepared by the crossover reactions of n-butyllithium (n-BuLi), poly(styryl)lithium (PSLi), and poly(isoprenyl)lithium (PILi) with the diphenylethylene analogue. The functionalization yields were over 87 mol.-% based on the results of ¹H NMR spectroscopic analysis. The number-average molecular weights of the polymers based on the ratio [gram of monomer]/[mole of initiator] are in good accordance with those observed from size exclusion chromatographic and ¹H NMR spectroscopic analysis (3,0 × 10³ ∼ 7,5 × 10³ g/mol).     

Kinetic and Mechanistic Studies of Carboxylic Acid–Bisoxazoline Chain‐Coupling Reactions

Kinetic studies of the reactions between a model carboxylic acid and bisoxazoline coupling agents, namely 2,2′‐(1,3‐phenylene)bis(2‐oxazoline) ( mbox ), 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) ( pbox ), and 2,2′‐(2,6‐pyridylene)bis(2‐oxazoline) ( pybox ), were carried out in bulk at 140–220 °C. A second‐order two‐step reaction mechanism was proposed and was verified by the experimental results. The results also indicate that the reactivity of the oxazoline groups is unchanged after the reaction of the other oxazoline group of the same coupling agent moiety, that is, oxazoline groups are equireactive. Rate constants and activation enthalpies and entropies were determined, allowing the comparison of bisoxazoline reactivity. The following reactivity order was found: pybox > mbox > pbox . The formation of a stabilized protonated complex is postulated to explain the much higher reaction rate observed with the new coupling agent pybox .

Variation of the experimental concentrations of reactants and reaction products versus time.     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 5. Synthesis of Star Polymers by Reactions of End‐Functionalized Polystyrenes with Chloromethylphenyl Groups with Polymer Anions Consisting of Two Polymer Chains

Well‐defined five‐arm star polymers, having different arms in molecular weight or composition, were synthesized by linking reactions of end‐functionalized polystyrenes with two chloromethylphenyl (CMP) groups and polymer anions consisting of two identical or different polymer chains. The polymer anions were prepared by coupling living anionic polymers of styrene or isoprene with 1,1‐diphenylethylene (DPE)‐end‐functionalized polymers. They were then reacted in situ with the CMP‐end‐functionalized polystyrenes to afford heteroarm star polymers of the AA′₂A″₂, AA′₂B₂, and AB₂C₂ types where the A, B, and C segments were polystyrene, poly(a‐methylstyrene), and polyisoprene, respectively. ¹H NMR spectroscopy, SEC, vapor pressure osmometry (VPO), and static light scattering measurements evaluated the well‐defined architecture of these polymers.     

Oxidative coupling polymerization of bisphenols

The oxidative coupling reactions of 4.4′-isopropylidene-bis-(2-methyl-6-tert-butylphenol) or 4.4′-isopropylidene-bis-(2-tert-butylphenol) with aqueous alkaline solution of potassium ferricyanide were found to give polymeric products (mol. wt. ca. 4500) which show self-curing reaction by heating. By comparing their spectral data with those of their model compounds, it was found that they contain the cyclohexadienone (o-quinol ether) structure which contributes to the self-curing reaction.     

Synthesis of low molecular weight poly(N-acryloylmorpholine) end-functionalized with primary amino groups,and its use as macromonomer for the preparation of poly(amidoamines)

Amphiphilic oligomers of poly(N-acryloylmorpholine) terminated at one end by primary amino groups have been prepared by free radical polymerization of the corresponding monomer, N-acryloylmorpholine, in the presence of cysteamine (2-mercaptoethylamine) as chain-transfer agent. The polymerization reaction was performed in aqueous media at acidic pH, in order to avoid any hydrogen-transfer addition reaction the the acrylic double bonds by the SH or NH₂ groups present in cysteamine. The chain-transfer constant of cysteamine towards N-acryloylmorpholine, under the conditions we used, was found to be very close to 1. The aminated poly(N-acryloylmorpholine) oligomers were found to behave as true macromonomers in polyaddition reactions with a diacrylamide, leading to new poly(amidoamines) carrying poly(N-acryloylmorpholine) chains as side substituents.     

Studies on functional diene oligomers with an amino end group, 2. Reaction mechanism of the isoprene oligomerization

Lithium diisopropylamide, in the presence of diisopropylamine, initiates the polymerization of isoprene to form oligomers having one diisopropylamino end group. These oligomers 1 a , formed in the early stages of the reaction, are considered to carry out the chain termination (or metalation) reaction. Results of mechanistic studies of the chain termination (or metalation) reaction in isoprene oligomerization in the presence of various types of allylamine homologues, as low molecular weight model compounds for 1 a are presented. The presence of a cis-methyl group with respect to the amino methylene group was found to be essential for the low molecular weight model compounds to exhibit large reactivity in the chain transfer reaction. Oligomers with amino end groups neither have to possess a cis-methyl group nor an allylamine structure to be active. A number of results showed that the driving force for the metalation reaction of oligomers with amino end groups is different in nature from that of the lowmolecular-weight allylamine homologues. A possible mechanism for the metalation reaction of these oligomers is discussed in terms of a hydrophobic interaction with the growing chain.     

Studies on the hydrolysis reaction of model substances of cellulose in the presence of polymer catalyst, 2. Effect of inorganic salts on the hydrolysis rate of dextrin catalyzed by poly(vinyl alcohol-co-vinylsulfonic acid)

The effect of inorganic salts on the hydrolysis rate of dextrin catalyzed by poly(vinyl alcohol-co-vinylsulfonic acid) was studied. The reaction is enhanced by addition of sodium chloride and potassium nitrate, and retarded with sodium sulfate and potassium sulfate. It may be presumed that in the presence of large amounts of salts the acidity is a predominant factor for the hydrolysis rate of dextrin in the present system, since it was found that the rate shows a linear relationship with the pH of the reaction mixture, and that the logarithm of the reaction rate was proportional to the ionic strength at values > 0,5 moll^?1. The difference in the reaction rates catalyzed by the copolymer or sulfuric acid was diminished with addition of salt, having no relation to whether the reaction rate was enhanced or retarded. Activation parameters of these reactions in the presence of salt were investigated, and it was found that the rate acceleration obtained by addition of salt was due to the increase in entropy of activation, although the enthalpy of activation was also increased. These effects are quite different from that observed in the rate acceleration by introducing hydroxyethyl units into the copolymer, suggesting that the reaction mechanisms for both rate acceleration effects are quite different, as can be inferred from the isokinetic relationships.     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 9. Radical Coupling Reaction of 1,1‐Diphenylethylene‐Functionalized Polymers with Potassium Naphthalenide and Its Application to Syntheses of In‐Chain‐Functionalized Polymers and Star‐Branched Polymers

Radical coupling reactions of both 1,1‐diphenylethylene (DPE)‐chain‐end‐ and DPE‐in‐chain‐functionalized polymers with potassium naphthalenide have been studied under the conditions mainly in THF at –78°C. Chain‐end‐functionalized polymers having M̄_n values of less than 10 kg/mol were very efficiently coupled in more than 90% yield to afford the polymeric dianion that were dimeric coupled products with two 1,1‐diphenylalkyl anions in the middle of the chains. However, the dimer yield decreased with increasing the molecular weight. The dimer was obtained in 59% yield with use of the chain‐end‐functionalized polymer having M̄_n of 33.9 kg/mol. Well‐defined in‐chain‐functionalized polymers with two benzyl bromide and DPE moieties each have been successfully synthesized by the reaction of the polymeric dianion thus obtained with 1‐(4‐bromobutyl)‐4‐(tert‐butyldimethylsilyloxymethyl)benzene and 1‐[4‐(4‐bromobutyl)phenyl]‐1‐phenylethylene, respectively. The radical coupling reaction of in‐chain‐functionalized polymers with DPE (M̄_n ca. 20 kg/mol) with potassium naphthalenide also proceeded efficiently to afford the coupled products that were A₂A′₂ and A₂B₂ four‐arm star‐branched polymers with well‐defined structures (M̄_n ca. 40 kg/mol).     

Studies of the autoxidation of phenols catalyzed by the cobalt(II) complex of disodium N,N′-bis(salicylidene)-ethylenediamine-5,5′ -disulfonate bound to colloidal anion exchange resin

To overcome mass transfer limitations which are usually encountered on immobilizing active catalysts, cationic latex particles were used as support for the cobalt(II) complex of disodium N,N′-bis(salicylidene)ethylenediamine-5,5′-disulfonate ( 1 ). The cationic latex 2 was prepared by emulsion copolymerization of chloromethylstyrene (m/p-isomer mixture 60/40) and divinylbenzene (m/p-isomer mixture) followed by treatment with trimethylamine. The latexbound catalyst from 1 and 2 was found to considerably increase the reaction rate of the autoxidation of 2,6-di-tert-butylphenol in water as compared with the conventional polymer-free system. Reaction products were identified as the oxidative coupling product 3,3′,5,5′-tetra-tert-butyldiphenoquinone (3,3′,5,5′-tetra-tert-butyl-4,4′-dioxo-1,1′-bicyclohexa-2,5-dienylidene) and 2,6-di-tert-butyl-1,4-benzoquinone. All reactions showed an induction period before the start of dioxygen consumption. The rate of autoxidation in the three-phase mixtures of water, latex particles, and phenol droplets was not affected significantly by the method of mixing. The reaction rate increased as the concentration of 1 increased. Increasing the partial pressure of dioxygen in the range between 0,25 and 1,0 atm (2,53. 10⁴ – 1,01. 10⁵ Pa) gave a small increase in rate. The colloidal latex catalyst from 1 and 2 showed some loss of activity after successive runs.     

New polymer syntheses, 36. Functionalized aromatic polyethers derived from 4′-substituted 2,6-difluorobenzophenones

Toluene, anisol, thioanisol, 4-phenoxyacetophenone and N,N-diacetyl-4-phenoxyaniline were subjected to a Friedel-Crafts acylation with 2,6-difluorobenzoyl chloride. The resulting 4′-substituted 2,6-difluorobenzophenones 1a – e were condensed with trimethyl silylated Bis-phenol-A ( 2 ) to yield homopolyethers with pendant functional groups. A series of copolyethers was analogously prepared by concondensation of 4′-substituted 2,6-difluorobenzophenones with a diphenol and 4,4′-difluorobenzophenone ( 4a ) or bis(4-fluorophenyl) sulfone ( 4b ), and another series by cocondensation of 2 with mixtures of 4′-substituted 2,6-difluorobenzophenones and 2,6-difluorobenzonitrile ( 8 ) or 2,6-difluoropyridine ( 9 ). All polyethers were characterized by inherent viscosities, elemental analyses and DSC-measurements. In individual cases GPC-measurements, thermomechanical and thermogravimetric analyses were conducted. The quantitative polymer-analogous oxidation of methylthio groups into methylsulfinyl and finally into methylsulfonyl groups is demonstrated.     

Introduction of oxygen function into isoprenoid systems by means of Botrytis cinerea (Persoon)

The introduction of oxygen functions into (±)- 1 -( 2′,2′,3′ -trimethyl- 3′ -cyclopenten-1′ -yl)-propan-2-one [(±)- 1a ], (±)- 1- ( 2′,2′,3′ ,-trimethyl-3′-cyclopenten-1′ -yl)-butan-2-one [(±)- 1b ], and (±)- 1 - (2′, 3′, 3′-trimethyl-3′ -cyclopenten-1′ -yl)-pentan-2-one [(±)-1c)] by Botrytis cinerea was carried out by hydroxylation in α position with respect to the double bond, or by epoxidation of the double bond itself. The main products had the hydroxy group at the methyl on the double bond. Simultaneously, a hydroxylation at the C′-5 position in 1a and 1b was observed. In 1e , an additional hydroxylation occurred at the C-4 position of the side chain. All the reactions were enantiospecific.     

Liquid crystalline poly(β-aminoester)s containing different mesogenic groups

Four series of new poly(β-aminoester)s based on different mesogenic units and amino spacers were prepared and their properties examined. The polymers were obtained by a Michael-type polyaddition reaction of the diamines piperazine ( 5a ), 2-methylpiperazine ( 5b ), N,N′-dimethylhexamethylenediamine ( 5c ), and 4,4′-trimethylenedipiperidine ( 5d ) to diacrylates containing the anisotropic group, trans-4,4′-vinylenedi-p-phenylene diacrylate ( 1 ), 4-(4-acryloyloxybenzylideneamino)phenyl acrylate ( 2 ), 4,4′-diphenylylene diacrylate ( 3 ), and 4,4′-azoxydi-p-phenylene diacrylate ( 4 ). The mesophase behaviour of the resulting polymers 6–9 was strongly influenced by the nature of both the anisotropic and spacer groups. The 4,4′-azoxydi-p-phenylene unit appeared to be the most efficient in promoting liquid crystal properties, whereas no mesophases could be observed in polymers incorporating the 4,4′-biphenylylene unit. Doping of poly(β-aminoester)s, based on 4,4′-azoxydi-p-phenylene units, with a low-molar-mass cholesterogen allowed to obtain cholesteric structures extending over wide ranges of temperature. The molecular weight of the polymers was found to play a role in determining thermotropic mesomorphism by affecting the melting temperature of the polymer. In this context, some non-macromolecular model compounds were analyzed in respect of their thermal behaviour.     

Roles of TraI protein with activities of cleaving and rejoining the single-stranded DNA in both initiation and termination of conjugal DNA transfer

Background:

The plasmid R100 encodes the TraI protein, which is required for conjugal DNA transfer. TraI has the activity of site- and strand-specific nicking of the supercoiled plasmid DNA. The molecular mechanism of this specific nicking, which is supposed to be the initiation reaction of DNA transfer, is not understood.

Results:

We have demonstrated that TraI has the ability to cleave the single-stranded DNA at the same site as the nicking site (nic) in a region, which we here refer to as sbi. The product contained the TraI protein which was covalently linked to the newly generated 5′ end of the nicking reaction. Both the cleaving and nicking reactions took place under almost the same conditions and required the presence of the sbi region. DNase I-footprinting analysis revealed that the TraI bound to the single-stranded DNA of the sbi region. TraI did not cleave the double-stranded DNA fragment, but it did cleave the double-stranded DNA with a single-stranded DNA portion in the sbi region. KMnO₄ mapping analysis revealed that TraI can melt the sbi region in the supercoiled DNA to generate a single-stranded portion. We have also demonstrated that TraI was able to rejoin the cleaved products. The rejoining reaction required the 5′ end of one cleaved product with the TraI covalently attached and the 3′ end of the other product containing the sbi region.

Conclusions:

Our results demonstrate that the nicking reaction—the initiation reaction of DNA transfer—is actually the cleaving reaction of the single-stranded DNA. TraI, which has both cleaving and rejoining activities, is thought to be involved in the termination of DNA transfer, to give a copy of the conjugative plasmid by joining the 5′ end, which is generated by the initiation reaction, with the 3′ end, which will be generated upon cleavage of the sbi region appearing after one round of the rolling circle replication of the plasmid.