Hydroboration,haloboration and phenylboration polymerizations

A polyaddition between diene and monoalkylborane produced a polymer consisting of C-B bonds in the main chain. The resulting organoboron polymers can be used as a novel type of reactive polymers. On the other hand, hydroboration polymerization of dicyano compounds produced air-stable poly(cyclodiborazane)s having B-N four-membered rings via dimerization of iminoborane species. Poly(organoboron halide)s were prepared either by haloboration polymerization between diynes and boron tribromide or by hydroboration polymerization of dienes with monobromoborane. Furthermore, phenylboration polymerization of diynes or diisocyanates gave new organoboron mainchain polymers.     

Poly(iminoborane)s: An Elusive Class of Main‐Group Polymers?

The significance of inorganic main‐group polymers is demonstrated most clearly by the commercial relevance of polysiloxanes (silicones). Organoboron‐based materials such as π‐conjugated organoborane polymers and BN‐doped polycyclic aromatic hydrocarbons are currently attracting considerable attention. Surprisingly, poly(iminoborane)s (PIBs; [BRNR′]_n), that is, the parent unsaturated BN polymers, which are formally isoelectronic to polyacetylene, have not been convincingly characterized thus far. Herein, we present the synthesis and comprehensive characterization of a linear oligo(iminoborane), which comprises a chain of 12–14 BN units on average. With our synthetic approach, unwanted side reactions that result in borazine formation are effectively suppressed. Supporting DFT and TD‐DFT calculations provide deeper insight into the microstructure and the electronic structure of the oligomer.     

Poly(cyclodiborazane)s

This paper summarizes our recent works on the synthesis and properties of the organoboron polymers, especially poly(cyclodiborazane)s. The polymers consist of boron–nitrogen four-membered rings, and are highly stable against air and moisture. The obtained polymers exhibited interesting properties as a novel type of π-conjugated polymers with intramolecular charge transfer structure. Their stability and potential as functional materials would be important and informative both in industry and boron chemistry.     

Cyclic imino ethers — Polymerization chemistry and polymer characteristics

This paper describes recent developments in polymerization of cyclic imino ethers, 2-oxazolines and 5,6-dihydro-4H-1,3-oxazines, which have been performed mainly in our laboratory. Cationic ring-opening polymerizations of these two kinds of monomers gave poly(N-acylethylenimine)s and poly(N-acyltrimethylenimine)s, whose hydrolysis produced linear poly-ethylenimine and poly(trimethylenimine), respectively. The mechanism of the polymerization is mainly governed by the nature of monomer and of the counter anion derived from initiator. There are two types of stable propagating species; cyclic onium species and covalent alkyl halide species. In a specific case, e.g., the polymerization of 5-methyl-2-oxazoline with MeI initiator, both ionic and covalent species are involved in equilibrium and propagate concurrently. Then, a new terminology of “Electrophile Polymerization” has been proposed as a broader expression including cationic and covalent propagating species. By utilizing living nature of the cyclic imino ether polymerization, block copolymerizations between these monomers were performed. A poly(cyclic imino ether) chain becomes hydrophilic or lipophilic depending on the monomer. Product AB and ABA type block copolymers were soluble in water and showed excellent surface properties reflected by values of surface tension (γ), when A (or B) and B (or A) are hydrophilic and lipophilic. Thus, various nonionic polymer surfactants of block and graft type have been prepared from cyclic imino ethers. Finally, poly(N-acetylethylenimine) chain showed good compatibility with poly(vinyl chloride). Cellulose diacetate and poly(vinyl chloride) are not miscible, but cellulose diacetate g-poly(N-acetylethylenimine) is miscible with poly(vinyl chloride), the graft chain acting as a “compatibilizer”.     

Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-b-PEG-b-CL) and poly(DTC-b-CL-b-DTC)

PCL possesses a wide range of medical applications, such as tissue engineering and controlled drug release, because of its good biodegradability and miscibility. In order to extend the use of PCL, researchers have been exploring its structural and chemica…     

Electroless deposition of poly(2-alkoxyaniline)s

The in situ deposition of poly(2-alkoxyaniline)s onto oxide surfaces is reported. It is demonstrated that the identity of the substrate can have a pronounced effect on the polymerization rate of these substituted polyanilines. Poly(2-alkoxyaniline)s deposit efficiently onto indium-doped tin oxide (ITO), but deposition onto quartz proceeds slowly. The critical stage in the deposition process is shown to be polymerization of the adsorbed oligomeric species. When this polymerization process is catalyzed by the surface, polymer growth is enhanced, and we find that conducting substrates mediate this apparent catalytic process. We demonstrate selective deposition by growing poly(2-alkoxyaniline) adlayers onto patterned ITO/quartz substrates.     

Synthesis,characterization, and thermal properties of dendrimer‐star,block‐comb copolymers by ring‐opening polymerization and atom transfer radical polymerization

Novel and well‐defined dendrimer‐star, block‐comb polymers were successfully achieved by the combination of living ring‐opening polymerization and atom transfer radical polymerization on the basis of a dendrimer polyester. Star‐shaped dendrimer poly(?‐caprolactone)s were synthesized by the bulk polymerization of ?‐caprolactone with a dendrimer initiator and tin 2‐ethylhexanoate as a catalyst. The molecular weights of the dendrimer poly(?‐caprolactone)s increased linearly with an increase in the monomer. The dendrimer poly(?‐caprolactone)s were converted into macroinitiators via esterification with 2‐bromopropionyl bromide. The star‐block copolymer dendrimer poly(?‐caprolactone)‐block‐poly(2‐hydroxyethyl methacrylate) was obtained by the atom transfer radical polymerization of 2‐hydroxyethyl methacrylate. The molecular weights of these copolymers were adjusted by the variation of the monomer conversion. Then, dendrimer‐star, block‐comb copolymers were prepared with poly(L ‐lactide) blocks grafted from poly(2‐hydroxyethyl methacrylate) blocks by the ring‐opening polymerization of L ‐lactide. The unique and well‐defined structure of these copolymers presented thermal properties that were different from those of linear poly(?‐caprolactone). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6575–6586, 2006     

The Relationship of Reaction Temperature,Tg and Rich‐Syndiotacticity of Poly(alkyl methacrylate)s in Modified Microemulsion Polymerization

Nanoscale poly(alkyl methacrylate)s including poly(methyl methacrylate), poly(ethyl methacrylate), poly(cyclohexyl methacrylate), poly(iso‐butyl methacrylate) and poly(benzyl methacrylate) were prepared by a modified microemulsion polymerization procedure. NMR analysis suggested that these poly(methacrylate)s samples were higher in syndiotactic content, lower in isotactic content and the glass transition temperatures (T_gs) of them were also higher than those reported in the literature. The tacticities of the poly(methacrylate)s, beside the restricted volume effect of nanoparticles during the modified microemulsion polymerization, were mainly influenced by the reaction temperature, the lower the reaction temperature, the higher the syndiotacticity of the products. The syndiotacticity of the product decreased obviously when the polymerization was carried out at a temperature far above the T_g of the resulting polymer. It was also shown that the tacticity of the polymer was affected by the monomer structure, a monomer with the bulkier alkyl side group would liable to result in a polymer with richer syndiotacticity. Possible mechanism of rich‐syndiotacticity was also discussed.     

Synthesis of Polyphenylene Thioethers Through Cationic Oxidative Polymerization

Polyaromatic sulfides are efficiently and conveniently prepared by cationic oxidative polymerization. Diphenyl disulfides are quantitatively polymerized to yield poly(p-phenylene sulfide)s as white powders whose structure predominately contains 1,4-phenylene sul-fide bonds. The disulfides are oxidized to phenylbis(phenylthio) sulfonium cations as active species of the polymerization. Repeating the oxidation and electrophilic reaction of the cation to the p-position of disulfides yields the polymer.     

Design and Application of Amphiphilic Polymeric Supports for Micellar Catalysis

In this contribution, the synthesis and application of amphiphilic poly(2-oxazoline)s with covalently bound transition metal catalysts for reactions in aqueous media is described. In the first example, bipyridine moieties were introduced via living ring-opening polymerization of functionalized oxazoline monomers and the resulting block copolymers were used as macroligands for ATRP (atom transfer radical polymerization) using Cu(I)Br as active metal species. Furthermore, the fixation of a chiral biphosphane and its use for enantioselective hydrogenation of enamides is presented as well as the fixation of a ruthenium catalyst. The latter one is used for polymerization of diethyl dipropargylmalonate (DEDPM), and represents the first example of an alkyne polymerization using a ruthenium catalyst. In the case of the polymers stable latex particles were obtained     

Living block copolymerization of phenyl vinyl sulfoxides and characterization of a stereogradient polymer

The polymerization of phenyl vinyl sulfoxide in blocks of increasing enantiomeric excess was carried out. Portions of the polymer were removed after each charge of monomer was consumed. The poly(phenyl vinyl sulfoxide)s were characterized by gel permeation chromatography and nuclear magnetic resonance spectroscopy. Reduction of the poly(phenyl vinyl sulfoxide)s to poly(phenyl vinyl sulfide)s permitted assignment of the polymer stereochemistry and verification that stereogradient polymers were formed.     

FTIR快速跟踪聚氨酯脲的反应注射成型研究

ＦＴＩＲ快速跟踪聚氨酯脲的反应注射成型研究罗宁，潘肇琦，王得宁，应圣康（华东理工大学材料科学研究所，上海，２００２３７）关键词聚氨酯脲，红外光谱，反应注射成型，动力学，相分离反应注射成型（ＲＩＭ）是生产聚氨酯制品的重要技术。以二醇扩链的聚氨酯的ＲＩＭ...     

Kinetic study of poly(ethylene oxide-b-2-methyl-2-oxazoline) diblocs synthesis from poly(ethylene oxide) macroinitiators

The synthesis of poly(ethylene oxide-b-2-methyl-2-oxazoline) (PEO-POXZ) block copolymers was carried out by the polymerization of 2-methyl-2-oxazoline (MeOXZ) from monomethoxy poly(ethylene oxide) macroinitiator. The initiating functions were 4-chloromethylbenzoate or tosylate groups. The functionalization of α-methoxy-ω-hydroxy PEO was optimized by adjustment of the reaction temperature. The duplication side reaction was investigated in the case of tosylate functionalization. The determination of the propagation rate constants of the MeOXZ polymerization showed that the presence of the PEO chains decreased the propagation rate constant in the case of active species under the form of oxazolinium ions, while it increased the propagation rate constant in the case of covalent active species, most probably by partial ionization.     

Studies on ceric–thiol-initiated aqueous vinyl polymerization with particular reference to end groups in poly(methyl methacrylate)

Ceric-thiol systems are good initiators for the acid aqueous polymerization of some water-soluble Vinyl monomers although not for styrene (in aqueous emulsion) and vinyl acetate. Thiols used are 2-mercaptoethanol, thioglycolic acid, 2-mercaptoethylamine hydrochloride, and L -cysteine hydrochloride. The polymerization proceeds through a radical mechanism. End-group analysis of poly(methyl methacrylate) obtained by initiation with various ceric-thiol systems has been carried out using Palit's dye testes. Hydroxyl, carboxyl, and amine end groups (to the extent of about one per polymer molecule) were incorporated in poly(methyl methacrylate)s obtained by initiation with 2-mercaptoethanol, thioglycolic acid, and 2-mercaptoethylamine hydrochloride, respectively, each in combination with Ce⁴⁺ ions; both amine and carboxyl end groups were obtained using C⁴⁺/L -cysteine hydrochloride initiator system. From the end-group results, the initiating species have been identified and the initiation mechanism prooposed. The probable termination mechanism also has been discussed.     

Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-<Emphasis Type="Italic">b</Emphasis>-PEG-<Emphasis Type="Italic">b</Emphasis>-CL) and poly(DTC-<Emphasis Type="Italic">b</Emphasis>-CL-<Emphasis Type="Italic">b</Emphasis>-DTC)

The ring opening polymerization of ε-caprolactone (CL) was initiated by glycol and yttrium tri(2,6-di-tert-butyl-4-methylphenolate)s (Y(OAr)₃), preparing dihydroxy-capped poly (ε-caprolactone) (PCL) with controllable molecular weight. ¹H NMR and SEC analyses indicate that two kinds of active species and corresponding PCL with different structures exist in the system. Increasing the ratio of glycol to Y(OAr)₃ benefits the formation of monofunctional active species. However, poly(ethylene glycol) (PEG)/Y(OAr)₃ system only contains sole bifunctional active species to synthesize copolymer of CL with PEG (poly(CL-b-PEG-b-CL)). Dihydroxycapped PCL as macroinitiator can further initiate the polymerization of 2,2-dimethyltrimethylene carbonate (DTC). Thus, triblock copolymer of CL with DTC (poly(DTC-b-CL-b-DTC)) has been prepared.     

New regiosymmetrical dioxopyrrolo- and dihydropyrrolo-functionalized polythiophenes

[structure: see text] We present the synthesis of two N-alkylated poly(dioxopyrrolothiophene)s and two N-alkylated poly(dihydropyrrolothiophene)s with potential application in the field of conducting polymers. The polymers are synthesized from the corresponding 2,5-dibromothiophenes by an Ullmann-type polymerization and a Stille-type polymerization, respectively. The two N-alkylated poly(dihydropyrrolothiophene)s are the first examples of amino-functionalized polythiophenes built from regiosymmetrical thiophene monomers.     

Synthetic studies toward the pyran core and the amide side chain of psymberin

A synthetic approach to the polysubstituted pyran core and amide side chain of psymberin (irciniastatin A) using stereoselective organoboron methodology is described. An advanced oxyranyl pyran intermediate was prepared using a catalytic enantioselective and diastereoselective three-component reaction involving first an inverse electron-demand hetero [4+2] cycloaddition between 3-boronoacrolein pinacolate and 1-ethoxy-2-methylpropene, followed by an allylboration of ethyl glyoxylate. The amide side chain was prepared highly efficiently using the first example of a doubly diastereoselective allylboration of a chiral α-alkoxy aldehyde under the Lewis acid-catalyzed reaction manifold.     

Synthesis and chemical recycling of novel poly(ester-urethane)s using an enzyme

A series of enzymatically recyclable poly(ester-urethane)s consisting of a biodegradable diurethane moiety as a hard segment and an ester moiety as an enzymatically cleavable linkage was chemo-enzymatically prepared by two routes. The poly(ester-urethane) was prepared by a) the ring-opening polymerization of a cyclic ester-urethane monomer synthesized via the transesterification reaction of biodegradable diurethanediol and dicarboxylate ester using lipase and b) the direct polycondensation of a diurethanediol and a dicarboxylate ester. A significantly higher molecular-weight poly(ester-urethane) having the highest molecular weight (Mw) of 101,000 was produced by the ring-opening polymerization of the cyclic ester-urethane monomer when compared with that produced by the polycondensation of the dicarboxylate ester with diurethanediol. The poly(ester-urethane) was readily degraded by lipase into the corresponding cyclic oligomers; the oligomers were readily repolymerized by the ring-opening polymerization using lipase for chemical recycling.     

Poly(p‐phenylene iminoborane): A Boron–Nitrogen Analogue of Poly(p‐phenylene vinylene)

Substitution of selected CC units in π‐conjugated organic frameworks by their isoelectronic and isosteric BN units (BN/CC isosterism) has proven to be a successful concept for the development of BN‐doped polycyclic aromatic hydrocarbons (PAHs) with intriguing properties and functions. The first examples have just demonstrated the applicability of this approach to polymer chemistry. Herein, we present the synthesis and comprehensive characterization of the first poly(p‐phenylene iminoborane). This novel inorganic–organic hybrid polymer can be regarded as a BN analogue of the well‐known poly(p‐phenylene vinylene) (PPV). Photophysical investigations on the polymer and a series of model oligomers provide clear evidence of some π‐conjugation across the B=N bonds and extension of the conjugation path with increasing chain length. TD‐DFT calculations provide deeper insight into the electronic structure of the new materials.     

Effect of polarity of the medium on the stereospecific polymerization of propylene by ansa-zirconocene catalyst

Propylene was polymerized with rac-ethylene-bis (1-η⁵-indenyl)dichlorozirconium/methylaluminoxane in solvents of different polarity. The poly (propylene) formed was separated by solvent extraction; ¹³C-NMR and DSC measurements were made on the polymer fractions. The poly(propylene) in each solvent fraction has its characteristic molecular weight steric pentad distributions, melting transition temperature, and enthalpy for fusion irrespective of the polymerization medium. The results suggest that the medium dielectric constant does not affect the polymerization rate or the intrinsic stereoselectivity, propagation and chain transfer rates a given catalytic species but can alter the occurrence of steric insertion errors through shifting of distributions of the propagating species producing poly(propylenes) of different stereoregularities. © 1994 John Wiley & Sons, Inc.