氧负离子聚合在超支化聚合物合成中的应用

近年来,氧负离子聚合得到较快发展,单体种类已经由酯基的β位上含有供电性杂原子的甲基丙烯酸酯类扩展到环氧类、甲基丙烯酸羟酯类单体.氧负离子引发这两类单体聚合,可以得到新型结构的超支化聚合物.对氧负离子引发合成超支化聚合物的机理及其应用进行了综述.     

Ionic Polymerization of Vinyl Aromatic Monomers

The ionic polymerization of vinyl monomers possessing aromatic and heterocyclic functional groups has not been studied in any systematic fashion. Only in a few isolated cases have detailed mechanistic and structural studies been reported. The anionic polymerization of a number of vinylanthracene monomers has recently been investigated and some rationalization of this system is presented. The cationic and anionic polymerization of the N-, 3-, and 2-vinylcarbazole series of monomers is discussed in some detail. The important role of vinyl aromatic/vinyl heterocyclic monomers, i.e., diphenylethylene and the vinylcarbazoles, in elucidating the mechanistic aspects of cationic polymerization, “change transfer” polymerization, and photoionic polymerization is considered.     

温度对4-甲基丙烯酸2,2,6,6-四甲基哌啶醇酯与苯乙烯自由基共聚活性的影响

本文研究了4-甲基丙烯酸2,2,6,6-四甲基哌啶醇酯和苯乙烯在不同温度下的自由基共聚合反应。发现在石油醚、苯和二甲基甲酰胺等溶剂中,反应温度对共聚活性的影响不同。用NMR法测定了单体与溶剂的络合常数;计算了单体与溶剂相互作用的活化能和活化熵,依此对共聚活性与温度之间的关系进行了讨论。     

Reactivity of oxetane monomers in photoinitiated cationic polymerization

Studies of the onium salt photoinitiated cationic ring‐opening polymerizations of various 3,3‐disubstituted oxetane monomers have been conducted with real‐time infrared spectroscopy and optical pyrometry. The polymerizations of these monomers are typified by an extended induction period that has been attributed to the presence of a long‐lived tertiary oxonium ion intermediate formed by the reaction of the initially formed secondary oxonium ion with the cyclic ether monomer. Because the extended induction period in the photopolymerization of these monomers renders oxetane monomers of limited value for many applications, methods have been sought for its minimization or elimination. Three general methods have been found effective in markedly shortening the induction period: (1) carrying out the photopolymerizations at higher temperatures, (2) copolymerizing with more reactive epoxide monomers, and (3) using free‐radical photoinitiators as synergists. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3205–3220, 2005     

Synthesis,characterization, and properties of novel aromatic bispropenyl ethers

Aromatic bispropenyl ethers are a new class of highly reactive thermosetting monomers that have been prepared and characterized. Two synthetic routes to their preparation have been developed. The first of these involves the base-catalyzed isomerization of bisallyl ether precursors that gives predominantly the Z bispropenyl ether isomers. The second method employs tris(triphenylphosphine)ruthenium(II) dichloride as an isomerization catalyst and produces predominantly the E isomers. Using these methods, a number of bispropenyl ether monomers containing different aromatic groups have been synthesized. The cationic polymerization of these novel monomers to give crosslinked network polymers using diaryliodonium salts as photo and thermal initiators has been studied.     

Syntheses of hydrophobically modified cationic hydrogels by copolymerization of alkyl substituted diallylamine monomers and their use as bile acid sequestrants

A novel class of cationic hydrogels bearing cyclic structures along the polymer backbone has been prepared and these hydrogels have been evaluated as bile acid sequestrants in vivo. The polymeric gels were prepared by the crosslinking cyclocopolymerization of hydrophobically modified dialkyldiallylammonium salts in the presence of different multifunctional crosslinking monomers. The roles of various crosslinking monomers, concentrations of crosslinking monomers, as well as alkyl chain length of dialkyldiallylammonium monomers on the physicochemical properties of the resulting hydrogels have been evaluated. From these preliminary in vivo studies it appears that these cationic hydrogels are excellent bile acid sequestrants and promising cholesterol lowering agents.     

Side-chain liquid crystalline polyesters derived from diethylmalonate and/or 1,3-propanediol

A series of azo monomers for polycondensation have been synthesized and characterized. These monomers, which contain electron-donor or acceptor substituents, have been condensed with aliphatic monomers to obtain two different series of aliphatic main-chain polyesters with pendant mesogenic groups. The polymers display nematic or smectic phases depending on the structural modifications of pendant mesogenic groups and the length of the flexible main-chain. In addition to these series, two polyesters with a high concentration of side pro-mesogenic groups have been synthesized. © 1996 John Wiley & Sons, Inc.     

Free volume properties of a linear soft polymer: a computer simulation study

Molecular dynamics simulation of a linear soft polymer has been performed and the free volume properties of the system have been analyzed in detail in terms of the Voronoi polyhedra of the monomers. It is found that there are only small density fluctuations present in the system. The local environment of the monomers is found to be rather spherical, even in comparison with liquids of atoms or small molecules. The monomers are found to be, on average, eight coordinated by their nearest geometric neighbors, including intra-chain and inter-chain ones. The packing of the monomers is found to be rather compact, in a configuration of 1900 monomers there are, on average, only three voids large enough to incorporate a spherical particle as large as a monomer, indicating that the density of the large vacancies in the system is considerably, i.e., by a few orders of magnitude lower than in molecular liquids corresponding to roughly the same reduced densities.     

Cationic photopolymerization of ambifunctional monomers

Certain metal-catalyzed hydrosilations have been found to occur in a highly regioselective manner which makes them useful for the preparation of unique classes of ambifunctional monomers. These monomers bear two chemically different functional groups within the same molecule. By selection of the appropriate functional groups it is possible to design monomers in which the functional groups react independently, copolymerize, or polymerize by different mechanisms. This article describes some recent results of the synthesis and polymerization of several novel types of ambifunctional monomers.     

Intermolecular potentials with flexible monomers

Most available intermolecular potentials assume rigid monomers. Such an assumption is a reflection of a trivial observation that if monomer degrees of freedom are considered, the dimensionality of an intermolecular potential increases dramatically even for few-atom monomers. This puts strict limits on the sizes of clusters with flexible monomers that can be treated by ab initio methods since the number of grid points needed to fit a potential surface quickly becomes enormous. Most of the literature flexible-monomer potentials were obtained from the so-called site-site rigid-monomer potentials by simply allowing the sites to move with atomic nuclei as the monomers are deformed. This simple atom-following approach has been investigated in the present work, using water dimer and Ar-HF as test systems, and shown to be not adequate. A method has been proposed which uses properties of isolated flexible monomers to improve upon the atom-following approach without performing any dimer calculations outside the rigid-monomer grid. The method is shown to give for Ar-HF a 3D representation of the dispersion energy that should be adequate for HF motion in the ground and first excited vibrational states.     

Synthesis and characterization of new chiral mesogenic monomers

New mesogenic monomers carrying substituted biphenylyl rings linked to acryloyl or methacryloyl moieties through straight or chiral flexible spacers have been synthesized. All the investigated monomers, independent of the side group chirality, have been found to form ordered smectic phases, most probably of the S₁ type. The asymmetric methyl substitution on the flexible spacer leads to an expansion of the temperature range of mesophase stability. The chiral monomers induce a helical structure when mixed with appropriate nematogens. The fingerprint texture of a contact mixture of the chiral methacrylate prepared in this work, with a nematic methacrylate synthesized previously, has been found not to change after UV-initiated polymerization.     

Synthesis and Photopolymerization of Silicon-Containing Multifunctional Oxetane Monomers

Abstract

A series of silicon-containing multifunctional oxetane monomers has been prepared and characterized. These monomers were compared among themselves and with other oxetane monomers with respect to their reactivity in photoinitiated cationic polymerization.     

Enantiomeric separation of chiral peptide nucleic acid monomers by capillary electrophoresis with charged cyclodextrins

Direct chiral separation of chiral peptide nucleic acid (PNA) monomers has been achieved for the first time by capillary electrophoresis (CE) with charged cyclodextrins as chiral selectors added to the electrophoretic buffer. Selectively modified 6-deoxy-6-N-histamino-beta-cyclodextrin and sulfobutyl ether-beta-CD were successfully used as chiral selectors for the enantiomeric separation of chiral monomers based on different aminoethylamino acids bearing thymine or adenine as nucleobases. Chiral separations were obtained at low selector concentrations (1-3 mM) with good enantioselectivity and resolution factors. Separations were optimized as a function of pH in order to exploit the effect of the electrostatic interactions between the oppositely charged selector and selectand. The method has been applied to the analysis of the enantiomeric excess of chiral monomers used for the solid phase synthesis of chiral PNA oligomers. CE chiral analysis showed that a very high enantiomeric purity was generally achieved in the synthesis of all monomers, except for histidine and aspartic acid based monomers in which ca. 10% of the "wrong" enantiomer was always present.     

Preparation of chiral amino acid materials and the study of their interactions with 1,1‐Bi‐2‐naphthol

The amino acid tryptophan has been converted into acrylamide monomers using L /D ‐tryptophan methyl ester forming the enantiopure chiral monomers. Attempts were made to polymerize these monomers via reversible addition fragmentation chain transfer (RAFT) polymerization to form poly(tryptophan). Unfortunately, this proved difficult, and instead, a postpolymerization modification route was used by first synthesizing poly(pentafluorophenyl acrylate) via RAFT, which was then substituted with L ‐tryptophan methyl ester to give poly(L ‐tryptophan). The interactions of the newly synthesized tryptophan monomers, as well as previously reported phenylalanine monomers, were studied in the presence of rac‐BINOL. It has been shown that the enantiomers of tryptophan have a stronger interaction with BINOL than phenylalanine and this has been attributed to the larger π system on the side chain. By monitoring the shifts and splitting of the phenolic protons of BINOL, it has been observed that S‐BINOL interacts more favorably with L ‐monomer enantiomers and R‐BINOL with D ‐monomer enantiomers. Similar interactions have also been seen with poly(phenylalanine) and the newly synthesized poly(tryptophan) materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

卟啉降冰片烯聚合物的合成、表征及性质研究

本文设计合成了卟啉的降冰片烯单体,采用Grubbs催化剂与长链烷基的降冰片烯单体开环易位聚合,直接得到了卟啉降冰片烯聚合物,通过紫外-可见吸收光谱、荧光光谱、电化学等手段研究了卟啉降冰片烯聚合物的性质,与小分子单体相比,所得卟啉高分子共聚物相当好地保持了卟啉应有的光物理、电化学等特性.     

Addition of dialkyl phosphites to difurfurylidene acetone

Phosphorus- and difuryl-containing reactive monomers have been synthesized by adding dimethyl or diethyl phosphite to difurfurylidene acetone. The monomers have been homo and copolymerized with difurfurylidene acetone affording polymers and copolymers with improved resistance to combustion.     

Synthesis, characterization and thermal degradation of functional benzoxazine monomers and polymers containing phenylphosphine oxide

Three phosphorus-containing bisphenol compounds, bis(4-hydroxyphenyl)phenylphosphine oxide (BHPPO), bis(4-hydroxyphenoxyphenyl)phenylphosphine oxide (BPPPO), and bis(4-hydroxyphenoxy)phenylphosphine oxide (BPHPPO) have been synthesized as starting materials for the synthesis of benzoxazine monomers. Benzoxazine monomers containing phenylphosphine oxide have been prepared and subsequently characterized by FT-IR and ¹H NMR. The monomers are thermally initiated and polymerized via ring-opening polymerization. Thermogravimetric analysis indicates that phosphorylation can have a profound effect on increasing char yield and on thermal degradation temperatures.     

Development of new cyclic olefin polymers for optical uses

New cyclic olefin polymers (COP) with a better balance of properties than those of conventional optical plastics have been developed by using norbornene monomers. The COP are prepared by ring-opening metathesis polymerization of norbornene monomers followed by complete hydrogenation of double bonds. The COP have practically been applied for optical uses such as lenses, prisms and optical discs.     

Influence of Comonomer Functional Groups on the Reactivity Ratios of Some Phenolic Monomers

The reactivity ratios of some halogen-substituted phenolic monomers have been determined by the linear graphical method of Kelen and Tüdöls. The nature of functional groups present in the comonomer influence the order of reactivity of p-chlorophenol, p-bromophenol, and p-iodophenol. The behavior of these monomers during copolymerization reaction has been interpreted in terms of 1) different degrees of resonance stabilization of the monomers, and 2) opposite polarization caused by the substituents present in the comonomer.     

Organic syntheses by means of metal complexes—XI : Copper complex catalyzed addition reactions of organic polyhalides to acrylic monomers

Telomerization, especially 1:2 adduct formation from organic polyhalides and acrylic monomers catalyzed by a copper complex has been studied. Reaction of carbon tetrachloride with acrylic monomers catalyzed by a copper salt gave a 1:2 adduct. Methyl trichloroacetate afforded a 1:2 adduct with acrylic monomers, addition of LiCl increased the yield. No 1:2 adduct was obtained from CHCl₃ even in the presence of LiCl. The 1:2 adduct formation mechanism is discussed.