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.     

Synthesis and ion-coupling reactions of telechelic polystyrene having cyclic onium salt groups

A series of mono- and bifunctional polystyrenes ( 1 c and 1 ′ c ) having 1-methylpyrrolidinium salt end groups were prepared through sequential derivatization, i.e., tosylation and quaternization reactions, of prepolymers having 3-hydroxypropyl groups ( 1 a and 1 ′ a ) produced by end-capping reactions of the relevant living polymers. The 1-methylpyrrolidinium salt end group was found to undergo a selective ring-opening reaction at 100°C by nucleophilic attack of a benzoate counter anion introduced by ion-exchange reaction. The ion-coupling reaction of 1 c and 1 ′ c with poly(styrene-co-acrylate salt) was found to take place upon coprecipitation of an equimolar mixture into methanol to afford ionically linked pseudo-graft and network products, respectively. The subsequent heat treatment, converting the ionic bond into a covalent one, results in branched and crosslinked polystyrene with predetermined structural parameters.     

New poly(carbobetaine)s made from zwitterionic diallylammonium monomers

A series of new hydrolytically stable poly(carbobetaine)s with varying distance between the ammonium and the carboxylate group was synthesized, excluding the presence of residual salt in the polymers, together with cationic and sulfobetaine analogues. The poly(carbobetaine)s show improved solubility compared to analogous poly(sulfobetaine)s, and are more hygroscopic. Their thermal stability depends strongly on the length of the spacer group separating the ammonium and the carboxylate group. The poly(carbobetaine)s are typically amorphous, but for long spacer groups, they exhibit a superstructure. They are capable of forming homogeneous blends with a number of inorganic salts, following the selectivity of the Hofmeister series, thus giving access to new organic-inorganic hybrid materials.     

Synthesis of star and model network polymers from poly(tetrahydrofuran)s with azetidinium end groups and multifunctional carboxylates

Star polymers with 2, 3 and 4 branches were synthesized in coupling reactions of poly(tetrahydrofuran) [poly(THF)] containing an azetidinium ring as single end group with di-, tri-, and tetrafunctional carboxylates, respectively. The coupling reaction proceeded by simple precipitation of the star polymer by addition of the polymer to an aqueous solution containing an excess of the corresponding sodium carboxylate. Model networks with 3 and 4 branches were produced by the same technique using poly(THF) with two azetidinium rings as end groups and tri- and tetrafunctional carboxylates, respectively.     

The mechanism of the initiation reaction of the cationic polymerization of tetrahydrofuran by stable cationic salts

The mechanism of the initiation reaction for the polymerization of cyclic ethers and lactones by triethyloxonium-, acetyl- and dioxolenium-salts was studied. Triethyloxonium salts initiate the polymerization of cyclic ethers simply by the alkyl exchange reaction. Cyclic esters react with triethyloxonium salts at both ether and carbonyl oxygens but the polymerization proceeds by the acyl-oxygen fission. The k_p value of the polymerization of THF by triethyloxonium salts is almost constant independent of gegenanion. Acetyl cation initiates the polymerization of THF partly by bonding mechanism, but dioxolenium salt initiates completely by bonding.     

Polymerization of lactams, 64. Nonactivated anionic polymerization of 2-pyrrolidone in the presence of quaternary ammonium cations

The effect of addition of quaternary ammonium halides was studied in the nonactivated polymerization of 2-pyrrolidone ( 1 ) initiated with the potassium salt of 2-pyrrolidone (2-oxo-1-pyrrolidinylpotassium) ( 2 ). The polymerization was accelerated upon small additions of Me₄NCl, whereas addition of Et₄NBr and Bu₄NBr rather had a retardation effect and reduced the molecular weight of polymer. The formation of the corresponding quaternary ammonium salts of 2-pyrrolidone in situ is analogous to the formation of the pure salts in their synthesis from the ammonium halides. The nonactivated polymerization of 1 initiated with the pure tetramethylammonium salt of 2-pyrrolidone ( 3 ) showed all kinetic features of other nonactivated polymerizations of 1 . High yields and molecular weights of poly(2-pyrrolidone) and a higher number of growth centers during polymerization are evidence of a higher dissociation of 3 dissolved in 1 in comparison with 2 as the initiator. The activation energy of polymerization activated with 3 (47,9 kJ · mol^?1 in the range 35 to 55°C) and the reaction order with respect to 3 (1,3 at 45°C) were determined.     

Synthesis and polymerization of epoxymethacrylates, 1. Catalysis and kinetics of the addition reaction of methacrylic acid and 2,2-bis[4-(2,3-epoxypropoxy)phenyl]propane

The kinetics of the addition reaction of methacrylic acid (1) and 2,2-bis[4-(2,3-epoxypropoxy)-phenyl]propane catalyzed by tertiary aliphatic amines, aromatic N-heterocycles and quaternary ammonium salts, respectively, was studied in bulk with equimolar amounts of functional groups from room temperature to 120°C. A reaction order of 1,5 with regard to the conversion of epoxy as well as carboxylic groups was observed. This can be explained assuming the formation of an ammonium alkoxide ion pair by the equilibrium reaction of an epoxy group with ammonium carboxylate and the irreversible consecutive reaction of the ion pair with (1) under formation of 2-hydroxyester groups and regeneration of ammonium carboxylate. The reaction rate constants increase linearly with the concentration of the catalyst and increase with increasing basicity of alkylpyridines. The advantage of the aromatic N-heterocyclic catalysts consists in their stability to peroxides which are ingredients of preparations together with the epoxy methacrylate Bis-GMA, e. g. in dental composites and adhesives.     

Zur Aufklärung des Initiierungsschrittes der kationischen Polymerisation von Tetrahydrofuran mit PF5

The course of the cationic initiation of the ring-opening polymerization of tetrahydrofuran (THF) with phosphorous pentafluoride ( 2 ) was investigated in the region above the ceiling temperature. In the reaction of 2 with THF and with 2-methyltetrahydrofuran (MTHF), respectively, generation of hexafluorophosphate from the initially formed donoracceptor complex of the cyclic ether and 2 was substantiated qualitatively as well as quantitatively. This process corresponds to the induction step of the THF polymerization. As the reaction product of 2 with THF, a dication, 1,1′-tetramethylene-bis(tetrahydrofuranylium) bis(hexafluorophosphate). ( 6 ), was isolated, the structure of which was verified by functional group analysis, chemical reactions, ¹H NMR and ³¹P NMR, respectively. POF₃, which is formed simultaneously, was proved qualitatively. Postulated intermediate reaction products remain below the traceable limit. From the results bifunctional oxonium ions are discussed to be the active species of the polymerization of THF with 2 , which initiate a bifunctional chain propagation.     

Synthesis of poly(α-malic acid) and its hydrolysis behavior in vitro

Biodegradable poly(α-malic acid) ( 7 ) was synthesized by means of ring-opening homopolymerization of malide dibenzyl ester ( 5 ), which is a cyclic dimer of β-benzyl malate. In order to obtain a high-molecular-weight biodegradable lactic acid type polyester having pendent modifiable groups, ring-opening copolymerization of malide dibenzyl ester with L -dilactide was applied to give poly(α-malic acid-co-lactic acid) ( 10 ). It was found from the results of hydrolysis of poly(α-malic acid) that the main-chain ester bonds were cleaved randomly and slowly in vitro.     

Über makrozwitterionen, 10. Versuche zur darstellung von makrozwitterionen aus α,ω-bifunktionellem poly(α-methylstyrol)

Some routes for the preparation of macrozwitter ions without polar groups in the polymer chain are discussed. With 3-dimethylaminopropyllithium as initiator and 1,3-propanesultone ( 2 ) as terminating agent, bifunctional poly(α-methylstyrene)s 4 could be obtained with a tert. amino- and a lithium sulphonato end group (molecular weight range ≈ 10³, bifunctionality > 90%). Both end groups were determined quantitatively, by elemental (N,S) and spectroscopic (IR and NMR) analyses as was done for the monofunctional model polymers. Although both end groups of the bifunctional polymers could be converted independently to the corresponding sulphonic acid group and the trimethyl ammonium iodide group, respectively, the macromitter ion 8 could not be obtained in the final reaction step: a rearrangement of the sulphonic acid 5 to the mitter ion 3 did unexpectedly not or scarcely occur, so that in the reaction with diazomethane the methyl sulphonate was preferentially formed instead of the betaine; in addition, an extensive loss of amino groups in the polymer was observed. With the poly(α-methyl styrene) 7 containing a quart, ammonium iodide and a lithium sulphonato end group, a degradation of the ammonium group was also found after the removal of the counter ions (I^⊕ by Ag₂O and Li^⊕ by cation exchange).     

Effects of pH on the supramolecular structure of polymeric molecular deposition films

A new kind of molecular deposition films was obtained by alternating deposition of a bipolar quaternary ammonium salt and poly(maleic acid monoester). The pH value of the cationic solution has great effect on the supramolecular structure of the polymeric ultrathin films. Two kinds of ultrathin films were formed according to a quasi-symmetrical model and a quasi-asymmetrical model.     

Anionic ring-opening polymerization of 2,2-dimethyltrimethylene carbonate

The anionic ring-opening polymerization of 2,2-dimethyltrimethylene carbonate in solution with sec-butyllithium as initiator was found to result under suitable conditions in a bimodal molecular weight distribution, vic. cyclic oligomers and a high-molecular-weight polymer. The concentration of cyclic oligomers approaches that of a ring chain equilibrium. In the kinetically controlled regime high polymer yields were obtained. Optimum reaction conditions for a polymer yield of 85 – 95% are a temperature of ?10°C, an initial monomer concentration of 10 weight-% and toluene as solvent. In THF the ring chain equilibrium is achieved readily. The ceiling temperature was determined to be ≈ 30°C. The homopolymer was characterized by spectroscopic, thermoanalytical and viscosity measurements. A high degree of crystallinity was observed.     

Simultaneous dehydrochlorination and film formation of a vinylidene chloride copolymer by aqueous-organic interface reaction

The interface reaction of a THF solution of a vinylidene chloride copolymer with an aqueous alkaline solution in the presence of a quaternary ammonium halide as a phase transfer catalyst affords a dehydrochlorinated polymer film with conjugated polyene structure. The degree of the reaction is dependent on the catalyst structure, and tetrabutylammonium bromide is the best among those used. KOH was found to be more effective than NaOH. The effects of the base and polymer concentration and of the nature of the solvent were also studied. The results are discussed in terms of the change of the rate of formation of ammonium hydroxide at the interface and of its diffusion in the organic phase. The doping of the obtained films with iodine vapor increases the electric conductivity up to 7 · 10^?4 S · cm^?1.     

Synthesis and free radical ring-opening polymerization of 2-methylene-4-phenyl-1,3-dioxolane

The cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( 3 ), was shown to undergo free radical ring-opening polymerization to produce the polyester, poly[γ-(β-phenyl)butyrolactone]. The monomer 3 was synthesized by an acetal exchange reaction of chloroacetaldehyde dimethyl acetal with styrene glycol in an 87% yield followed by dehydrochlorination of the resulting cis and trans-2-chloromethyl-4-phenyl-1,3-dioxolane ( 2 ) with potassium tert-butoxide in tert-butyl alcohol in a 70% yield. 3 was shown to undergo essentially quantitative free radical ring-opening at all temperatures from 60–150°C and also nearly complete regioselective ring-opening with cleavage to give the more highly stable secondary benzyl free radical. Even in free radical copolymerization with styrene, methyl methacrylate, vinyl acetate, or 4-vinylpyridine, 3 gives essentially complete ring opening to introduce an ester groups into the backbone of the addition copolymer. The structures of the polymers were established by elemental analysis and ¹H and ¹³C NMR spectroscopy.     

壳聚糖季铵盐在生物材料中的应用

壳聚糖季铵盐是壳聚糖的衍生物,不但拥有季铵盐的抗菌、抑菌、保湿性,还保留了壳聚糖的降解性及生物相容性,被广泛应用于各领域。将壳聚糖季铵盐引入生物材料中可有效提高生物材料抗菌等性能。本文将对壳聚糖季铵盐在骨组织工程支架材料、医用钛合金及生物载体近几年的研究做一综述,以期为壳聚糖季铵盐在生物材料中的应用提供参考。     

Synthesis and studies of some organic poly(ammonium phosphate)s, 1

Long chain organic poly(ammonium phosphate)s ( 1a – g and 2 ) were prepared by a precipitation technique by reaction of poly(lithium phosphate) with organic ammonium salts. Their compositions were established by nitrogen and phosphorus analyses and their polymeric nature was confirmed by molecular weight determinations via end group titrations and by the viscosity method. Studies of conductance at different concentrations indicated their polyelectrolytic behaviour. Paper chromatographic studies supplied additional evidence of a long chain polymeric structure, like Graham's salt and poly(lithium phosphate).     

Synthesis of poly(vinyl alcohol)-graft-poly(tetrahydrofuran)

The reaction of a living poly(tetrahydrofuran) (poly(THF)), prepared with methyl trifluoromethanesulfonate as an initiator, with 3-sodiopropoxydimethylvinylsilane was carried out to produce a uniform poly(THF) macromonomer with a vinylsilane end-group. Poly(vinyl acetate)-graft-poly(THF) of controlled graft segment length was then synthesized through radical copolymerization of this poly(THF) macromonomer with vinyl acetate. The subsequent saponification with NaOH in methanol provided poly(vinyl alcohol)-graft-poly(THF).     

Kinetics of the polymer-analogous reaction of poly[(methyl methacrylate)-co-(methacrylic acid)] with epichlorohydrin

Poly[(methyl methacrylate)-co-(glycidyl methacrylate)] (poly(MMA-co-GMA)) was obtained by polymer-analogous reaction of poly[(methyl methacrylate)-co-(methacrylic acid)] with an excess of epichlorohydrin (ECH) in the presence of a quaternary ammonium salt R₄NX as catalyst. The kinetics of the addition reaction and the consecutive transepoxidation reaction was studied at 50–90°C. The rate constant of the addition reaction is one order of magnitude higher with E₁ = 71 kJ · mol^?1 than that of the transepoxidation reaction with E₂ = 83 kJ · mol^?1. The rate constants rise linearly with increasing concentration of the catalyst R₄NX. The equilibrium constants K ≈ 2,3 of transepoxidation of glycidyl methacrylate (GMA) as well as of poly(MMA-co-GMA) both with 1,3-dichloropropane-2-ol were determined in butyl acetate and dimethylformamide as solvent at 80–100°C. During the reverse transepoxidation reaction of 3-chloro-2-hydroxypropyl methacrylate (CHPM) as well as of its MMA-copolymer with equimolar amounts of ECH, side products were formed from the beginning of the reaction and the equilibrium was not established. The addition of ECH to CHPM was observed as a side reaction.     

New thermo-crosslinking reactions of copolymers of phenyl methacrylates by use of polyfunctional epoxy compounds

Successful new thermo-crosslinking reactions of copolymers of various phenyl methacrylates by use of polyfunctional epoxy compounds were carried out in the film state at 100–150°C in presence of quaternary ammonium salts, quaternary phosphonium salts, tert-amines, or the crown ether dicyclohexyl-18-crown-6/potassium salt systems as a catalyst. Addition reactions of 4-nitrophenyl, 4-chlorophenyl or phenyl ester groups in the copolymers with ethylene glycol diglycidyl ether (EGGE) result in gel compounds without other side reactions. The rate of gel production of the copolymer having electron-attracting groups such as the 4-nitro group on phenoxide is faster than that of the other copolymers. It was also found that the rate of gel production of the copolymer is affected by the amount of phenyl methacrylate component in the copolymer, the glass transition temperature (T_g) of the copolymer, the structure of polyfunctional epoxy compounds as a crosslinking reagent, the length of alkyl chain in the catalyst, and the kind of counter anion of the catalysts, respectively.     

Topological Effects on Cyclic Co-Poly(ionic liquid)s Self-Assembly

Topological geometry of poly(ionic liquid)s (PILs), such as brush-like, knot-like, hyperbranched and randomly coiled, often exerts a strong influence on their self-assembly behaviors. As a primary topological form, the cyclic topology-derived effects have not been investigated on PILs, which concerns synergy of charges and zero chain end. Herein, linear and cyclic poly(ionic liquid) copolymers (co-PILs) with randomly distributed counter anions of B(Ph)₄⁻ and Br⁻ by a template method in combination with a follow-up partial anion exchange is prepared. The self-assembly phenomena of linear and cyclic co-PILs are studied in selective solvents, where the hydrophobic counter anions B(Ph)₄⁻ and hydrophilic counter anions Br⁻ aggregated to form cores and corona in the assembled nanospheres, showing the average size of cyclic co-PILs nanospheres is 46.2% smaller (≈120 nm) than linear co-PILs nano-assemblies (≈176 nm). Based on the CGMD simulations, the authors speculate that the spherical aggregates are formed by transitioning from micelles with gradient block-like structures, which formed by enriched hydrophobic counter anions in the core and enriched hydrophilic counter anions in the corona. These results indicate a novel synergy of topology effects and dynamic anion movements, as revealed by cyclic co-PIL self-assembly in this work.