含三氰乙烯基强吸电子基团的环氧树脂基非线性光学聚合物的合成

非线性光学聚合物材料及其在聚合物电光调制器中的应用是目前国内外研究的前沿。环氧树脂类聚合物具有很好的成膜性及可化学交联性能,是一类非常好的非线性光学聚合物的基体材料。本论文从分子设计的角度出发,将含三氰乙烯基强吸电子取代基及噻吩芳杂环共轭结构非线性光学生色团成功引入环氧树脂类聚合物,并在生色团侧基上引入甲基取代基。结果表明,苯胺残基中侧位甲基取代基对于先驱聚合物的亲电取代反应程度及最后聚合物的紫外-可见光最大吸收波长均有一定的影响,对于没有侧甲基的BP-TA-TC和一个侧甲基取代基的BP-3-TA-TC其官能化度均可以达到80%以上,而对于含两个甲基取代的BP-3,5-TA-TC先驱聚合物其官能化度则相对较低(低于10%)。随着甲基取代数目的增多,最后非线性光学聚合物的最大吸收波长也有不同程度的蓝移。     

Atropisomerism in the 2-arylimino-N-(2-hydroxyphenyl)thiazoline series: influence of hydrogen bonding on the racemization process

A series of original atropisomeric iminothiazolines 1 in which X = OH or (and) Y = OH were prepared from the corresponding methoxy precursors. The resolution of the atropisomeric enantiomers on chiral support is reported, and the barriers to enantiomerization are given. These barriers were determined either by off-line racemization studies or by treatment of the plateau-shape chromatogram during chromatography on chiral support. When X = OH, the barriers are quite low due to the development of a hydrogen bond between the proton of the OH group and the nitrogen of the imino group. For these compounds, plateau shape chromatograms were obtained during HPLC on chiral support. DFT calculations confirmed the occurrence of hydrogen bonding all along the rotation process and produced calculated barriers in close agreement with the experimental data. Compound 1i (OH, OH) in which both X and Y are hydroxy groups was particularly easy to prepare by demethylation with BBr3 of the dimethoxy precursor. Since the above-mentioned precursor is readily available from N,N'-bis(2-methoxyphenyl)thiourea and 1-chloropropan-2-one, 1i (OH, OH) is a good candidate for further functionalization. Atropisomerism in a 12-membered bridged bisether prepared from 1i (OH, OH) is reported as an illustrating example.     

One-Handed Helical Tubular Ladder Polymers for Chromatographic Enantioseparation**

Defect-free one-handed contracted helical tubular ladder polymers with a π-electron-rich cylindrical helical cavity were synthesized by alkyne benzannulations of the random-coil precursor polymers containing 6,6′-linked-1,1′-spirobiindane-7,7′-diol-based chiral monomer units. The resulting tightly-twisted helical tubular ladder polymers showed remarkably high enantioseparation abilities toward a variety of chiral hydrophobic aromatics with point, axial, and planar chiralities. The random-coil precursor polymer and analogous rigid-rod extended helical ribbon-like ladder polymer with no internal helical cavity exhibited no resolution abilities. The molecular dynamics simulations suggested that the π-electron-rich cylindrical helical cavity formed in the tightly-twisted tubular helical ladder structures is of key importance for producing the highly-enantioseparation ability, by which chiral aromatics can be enantioselectively encapsulated by specific π-π and/or hydrophobic interactions.     

Synthesis of chiral helical poly[p-(oligopinanylsiloxanyl)phenylacetylene]s and enantioselective permeability of their membranes

To develop better polymeric materials for optical-resolution membranes, we synthesized nine chiral phenylacetylenes containing pinanyl groups. We used them to investigate the effects of chemical structures, including the number and position of the chiral groups in the monomers, on the induction of chirality in the main chain during polymerization and on the degree of enantioselectivity in the permeation of the polymeric membranes. The monomers included six new chiral p-(oligomethylpinanylsiloxanyl)phenylacetylenes. The homopolymerizations of these nine monomers with a Rh complex produced high-molecular-weight polymers (molecular weight = 10⁵–10⁶). Of the five polymers with a chiral pinanyl group at the 1-position of each oligosiloxanyl group, all except for two polymers showed high molar ellipticity in the main-chain region in the circular dichroism spectra. This finding indicated that these polymers had a chiral helical main chain. The membranes fabricated from all the polymers synthesized in this study were high-quality, except for two polymers. All these membranes showed enantioselective permeabilities for two amino acids and an alcohol. The membranes from the polymers with a chiral helical backbone, a high content of pinanyl groups, no oligodimethylsiloxane moieties, or a combination of these showed good enantioselectivities (= 1.7–640) in permeation. We propose that the sense of the main-chain helicity determined the selectivity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4502–4517, 2004     

Diverse Approaches for Enantioselective C−H Functionalization Reactions Using Group 9 CpxMIII Catalysts

Transition-metal-catalyzed C−H functionalization reactions with Cp*M^III catalysts (M=Co, Rh, Ir) have found a wide variety of applications in organic synthesis. Albeit the intrinsic difficulties in achieving catalytic stereocontrol using these catalysts due to their lack of additional coordination sites for external chiral ligands and the conformational flexibility of the Cp ligand, catalytic enantioselective C−H functionalization reactions using the Group 9 metal triad with Cp-type ligands have been intensively studied since 2012. In this minireview, the progress in these reactions according to the type of the chiral catalyst used are summarized and discussed. The development of chiral Cp^x ligands the metal complexes thereof, artificial metalloenzymes, chiral carboxylate-assisted enantioselective C−H activations, enantioselective alkylations assisted by chiral carboxylic acids or chiral sulfonates, and chiral transient directing groups are discussed.     

Molecular interactions at the interface in blends of ester groups-functionalized polyolefins

Due to the apolarity of the aliphatic backbones, unmodified polyolefins are scarcely miscible with most of other polymers. The functionalization of preformed polyolefins is a way which has been successfully followed to improve the polymer miscibility. The functionalization of linear low density polyethylene (LLDPE) and ethylene-propylene copolymers (EP), with diethyl maleate (DEM) and dicumyl peroxide (DCP) as radical initiator, gives products containing up to 2–5 mol % of well defined functional groups (2-diethyl succinate). Intermolecular interactions of these functional groups are characterized by comparison with suitable low-molecular-weight structural models in the presence of different solvents containing acidic hydrogen atoms. On the basis of these indication evidences of interface molecular interactions in blends with halogenated polymers are described between the functionalized polyolefins and poly(vinyl chloride) (PVC), poly(vinylidene fluoride) (PVDF) or vinylidene fluoride-hexafluoropropene copolymer obtained in semiindustrial Brabender mixers. It is shown that a smooth functionalization of the polyolefins can modify the phase behaviour and structure of these systems. The FT-IR microanalysis supports the occurrence of partial miscibility phenomena which can be accounted for by specific intermolecular interactions involving the inserted functional groups and occurring mainly at the interfaces between domains of polyolefins and of the halogen-containing polymers.     

Controlled Positioning of Activated Ester Moieties on Well‐Defined Linear Polymer Chains

The successful sequence‐controlled installation of an activated ester using a newly designed monomer pentafluorophenyl 4‐maleimidobenzoate is demonstrated. Pentafluorophenyl 4‐maleimidobenzoate is kinetically installed at different stages of a nitroxide‐mediated polymerization, namely, near the α‐chain end and in the middle of a PS chain. In addition, successful installation of apolar and polar functional groups is achieved via post‐polymerization functionalization, which demonstrated the versatility of the synthesis of a universal precursor for locally functionalized polymers.     

Stannylated polynorbornenes as new reagents for a clean Stille reaction

New functionalized polynorbornenes have been obtained in good yields by vinylic copolymerization of norbornene with a (norbornenyl)SnBu(2)Cl monomer, catalyzed by [Ni(C(6)F(5))(2)(SbPh(3))(2)]. Subsequent functionalization produces a wide variety of polymers with different --SnBu(2)R groups (R=aryl, vinyl, alkynyl). The polymers can be used as R-transfer reagents in Stille couplings, thereby providing easy workup and separation of the polymeric tin byproducts from the coupling products. Tin contents of around 0.05 wt % are found in the Stille products. The stannylated polymers can be recycled and reused with good efficiency.     

Exploration of mandelic acid-based polymethacrylates: Synthesis,properties, and stereochemical effects

Mandelic acid (MA) was utilized as a chiral biomass-based precursor to synthesize methacrylic monomers suitable for radical polymerization. A series of polymers were made that incorporated varying feeds of monomer stereopurity and the properties of these materials were investigated. High molar masses (>90 kg/mol) were achieved and the chirality in each polymer closely reflected the stereopurity of the monomer feeds. It was discovered that stereochemical effects had very little influence on the thermal and viscoelastic properties of the polymers produced, however, the steric bulk of the chiral pendants resulted in glassy, amorphous, and thermally stable materials with very low degrees of entanglement. The synthesis, thermal, and viscoelastic properties are discussed.     

Recent developments in the synthesis and functionalization of conducting poly(thiophenes)

The mechanism of the electropolymerization of thiophene derivatives has been investigated by varying the electrosynthesis conditions and the monomer structure. The results of these analyses led to the definition of optimized electrosynthesis conditions allowing the control of the electrical and electrochemical properties of poly(thiophenes). On the basis of these results, the properties of these polymers have been modified by means of a new one-step electrosynthesis of conducting composite materials and by the direct electropolymerization of tailor-made functionalized monomers. For this purpose, the steric conditions associated to the various possibilities of covalent derivatization have been analyzed, leading to the definition of a “functionalization space”, compatible with the preservation of high conductivity and electrochemical reversibility in the resulting polymers. This concept has been applied to the synthesis of highly conducting chiral poly(thiophenes) on which an effect of enantioselective molecular recognition has been demonstrated for the first time.     

Stereoselectivity in metallocene-catalyzed coordination polymerization of renewable methylene butyrolactones: from stereo-random to stereo-perfect polymers

Coordination polymerization of renewable α-methylene-γ-(methyl)butyrolactones by chiral C(2)-symmetric zirconocene catalysts produces stereo-random, highly stereo-regular, or perfectly stereo-regular polymers, depending on the monomer and catalyst structures. Computational studies yield a fundamental understanding of the stereocontrol mechanism governing these new polymerization reactions mediated by chiral metallocenium catalysts.     

Investigation of molecular and chiroptical characteristics of optically active functional vinyl copolymers possessing main-chain chirality

Optically active styrene-methyl methacrylate and styrene-methacrylonitrile copolymers were obtained by template assisted asymmetric copolymerization of 3,4-cyclohexyhdene-D-mannitol-1,2;5,6-bis-O[(4-vinylphenyl)boronate] ( 1 ) with the corresponding comonomers followed by removal of the template and deboronation. By polymer analog modification methods, several optically active functional copolymers were obtained starting with these copolymers. The resulting polymers were subjected to different types of spectroscopic analysis. Thus, the results obtained from IR, ¹³C-NMR and GPC were of great value for detailed structural analysis of these polymers providing both qualitative and quantitative informations in terms of mode and neatness of substitution and degree of functionalization. The chiroptical measurement results obtained from circular dichroic (CD) studies have been utilized to analyze precisely the substituent dependent local solution stereochemistry of these chiral polymers. © 1992 John Wiley & Sons, Inc.     

Effect of a lateral substituent on the mesomorphic properties of ferroelectric side chain liquid crystalline polysiloxanes

The synthesis of side chain liquid crystalline polysiloxanes containing oligooxyethylene spacers and ( S )-2-methylbutyl 4-\[(4-oxybiphenyl-4-yl)carbonyloxy]-3-fluorobenzoate mesogenic side groups is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements reveal liquid crystalline properties for all synthesized monomers and polymers. All three precursor olefinic monomers reveal cholesteric and smectic A phases. The olefinic monomer which contains two oligooxyethylene units in the spacer is the only one which reveals a twist grain boundary A phase and a blue phase, besides the cholesteric and smectic A phases. All three polysiloxanes present enantiotropic smectic A and chiral smectic C phases. The mesomorphic behaviours of the monomers and polymers are compared with those of the corresponding monomers and polymers without the lateral fluoro substituent. The results seem to demonstrate that incorporating a lateral fluoro substituent in the mesogenic cores of the monomers affects not only the mesophase thermal stability, but also the nature of the mesophases formed. However, incorporating a lateral fluoro substituent in the mesogenic cores of the polymers affects only the thermal stability of the mesophases formed. The lateral fluoro substituent has a more profound effect on the mesomorphic behaviour for the monomers than that for the polymers.     

Synthesis of Materials with Self-Ordering Chiral Macromolecules

The present work focuses on chirality, functionalization, and molecular shape to establish links between molecular architecture and the spatial organization of polymer chains in organic materials. The approach used was to synthesize chiral and racemic homologous polymers exhibiting a preference for extended chain conformations and having the strongly dipolar cyano group as a substituent of the stereogenic center. The strong dipole moment at the chiral center offered potential to combine strong long-range forces with chiral recognition. Electron and optical microscopies were our selected tools to probe three-dimensional structures, and nonlinear optics was used to measure the properties of the materials obtained. We found that the relative stereochemistry of the repeat unit dipole impacts significantly on global chain symmetry and its packing mode. Enantiomeric enrichment of chains changed hexagonally packed cylindrical molecules to board-like molecules which pack edge-to-edge in an orthorhombic lattice. Interestingly, enantiomeric enrichment of chains enhanced the second-order nonlinear optical susceptibility of films prepared from these macromolecules.     

Asymmetric Synthesis of Chiral Atropisomeric Bis‐Aryl Organophosphorus from Menthyl H‐Phosphinate

This review describes new methods for the synthesis of chiral monophosphine ligands with menthyl phenylphosphinate as a chiral auxiliary through asymmetric Suzuki‐Miyaura cross‐coupling reactions and asymmetric C–H functionalization. The chiral menthyl phenylphosphinate as a chiral auxiliary is easy to prepare and the menthyl group can easily be transformed into other functional groups, with the chiral center synchronously remaining. These methodologies provide highly efficient and practical strategies for the synthesis of novel axially chiral biaryl monophosphine oxides and their corresponding phosphines. Meanwhile, these reactions are easy to handle and exhibit wide scope for substrates with excellent diastereomeric ratios.     

Functionalization of polyolefins by reactive processing: influence of starting reagents on content and type of grafted groups

Previous studies carried out in our laboratory on the functionalization of ethylene polymers (homo and copolymers) through free radical processes, using mechanical mixers and/or extruders with diethylmaleate (DEM) and dicumyl peroxide (DCP), have shown that the presence of branched α-olefin blocks favours degradation versus functionalization and crosslinking whereas these last are more effective with linear ethylene blocks. In this contest the present paper reports about attempts to extend the same processes to propylene polymers by benefitting of the indications of previous results. In particular the one step functionalization of EPM with two or more different groups was carried through the use of different monomers. Moreover the procedure was extended to polypropylene thus obtaining a significant functionalization degree flanked by a remarkable decrease of molecular weight.     

Synthesis of chiral polybinaphthyls with novel conjugated chromophores

An efficient strategy has been developed to incorporate new chromophores into chiral binaphthyl polymers. The repeating units of these polymers are made of conjugated structures with strongly electron-donating amino groups at the both ends. These optically active materials contain the highest possible density of chromophores in a polymer chain since every repeating unit in these polymers is a chromophore. They are soluble in common organic solvents and can be easily processed. The spectroscopic properties of these polymers are studied. The structural similarity of the chromophores in these chiral conjugated polymers with those of two-photon absorbing molecules may lead to interesting optical properties.     

New liquid-crystalline polymers with chiral phases

Liquid-crystalline polyesters with cholesteric and probably chiral smectic C* phases were prepared using combined liquid-crystalline polymers (that is polymers with the mesogenic groups in the main chain as well as in the side groups). Copolyesters of these polymers and polymers with olefinic double bonds could be cross-linked retaining the liquid-crystalline phases. This resulted in cross-linked polymers with elastic properties.     

Study on new chiral liquid crystalline monomers and polymers containing menthyl groups

A series of new chiral monomers (M1–M4) and the corresponding siloxane polymers (P1–P4) containing menthyl groups were synthesised to establish the relationship between their structure and liquid crystalline properties. The effect of the mesogenic core rigidity and the spacer length on the phase behaviour of the monomers and polymers obtained in this study was discussed. The selective reflection of light for the chiral monomers was studied with UV-Vis spectrometer. Polarising optical microscopy, differential scanning calorimetry, X-ray diffraction and thermogravimetric analysis were used to characterise the phase behaviour and thermal stabilities. It was found that these chiral monomers and polymers were beneficial for the formation of the mesophases when a flexible spacer was inserted between the mesogenic core and terminal menthyl groups. M1–M3 showed enantiotropic chiral smectic C phase and cholesteric phase, and monotropic cubic blue phase on cooling cycle. M4 only showed cholesteric phase. P1–P4 showed a smectic A phase. With increasing the mesogenic core rigidity or decreasing the spacer length, the corresponding melting temperatures, glass transition temperatures and isotropic temperatures all increased.