Effect of chiral isosorbide groups on mesomorphic properties of side-chain liquid-crystalline polysiloxanes

Chiral side-chain liquid-crystalline (LC) polysiloxanes containing isosorbide groups were graft copolymerised with poly(methylhydrogeno)siloxane, a chiral LC monomer 6-(4-methoxy-benzoyloxy)-hexahydro-furo[3,2-b]furan-3-yl 4'-(4-undec-10-enoyloxy-benzoyloxy)-biphenyl-4-yl adipate and a nematic LC monomer 4'-(4-methoxy-benzoyloxy)-biphenyl-4-yl 4-(2-undec-10-enoyloxy-ethoxy)-benzoate. The chemical structures and LC properties of the monomers and polymers were characterised by use of various experimental techniques including Fourier transform infrared spectroscopy (FTIR), ¹H-nuclear magnetic resonance (NMR), element analyses (EA), differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction (XRD). All the chiral LC polymers showed LC properties with very wide mesophase temperature ranges and the chiral component in the LC polymer systems lead to the appearance of a cholesteric phase. The polymers bearing most chiral LC monomer component showed smectic phases by reason of regular structures in the polymer systems. With the increase of another nematic LC monomer in the polymers, the regular polymer structures were destroyed because of different chemical structures between the two kinds of LC monomers, leading to the disappearance of the smectic arrangement.     

Synthesis,polymerization, and thermal properties of a new acetylene-terminated schiff base

A new acetylene-terminated Schiff base monomer, N,N′-(1,4-phenylenedimethylidyne)-bis-(4-ethynylaniline) (PPP), was synthesized and was characterized by nuclear magnetic resonance and infrared spectroscopy. This monomer was then polymerized to yield a new polymer (PPPP) with alternating units of aromatic imine and diacetylene via an oxidative coupling polymerization of the acetylenic terminal groups. The monomer was also polymerized by thermal curing at elevated temperatures up to 400°C to afford a crosslinked polymer network without significant structural decomposition. Thermal properties and thermal reactions of the monomer and the polymers were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The polymers exhibit excellent thermal stabilities in an inert atmosphere. Electronic properties of the polymers are also discussed.     

SYNTHESIS, CHARACTERIZATION OF CHIRAL POLY（ESTER AMIDE）S DERIVED FROM L-ISOLEUCINE

A series of new optically active aromatic poly(ester arnide)s containing a chiral group in the side chain prepared from the p-toluenesulfonic acid salt of o,o‘-bis(leucyl)-hexanediol (TS^- LHD^ TS^-) and p-phthaloyl chloride and styrene-2,5-dicarbonyl chloride styrene have been synthesized by interfacial polymerization. The structure of the monomer is elucidated by FT-IR and elemental analysis. The thermal properties of the polymers were studied by DSC and TGA. The chiroptical properties of the above polymer have also been studied by circular dichroism (CD) spectroscopy. Results indicated that these polymers form helical structures.     

Enantiomer-selective Living Polymerization of <Emphasis Type="Italic">rac</Emphasis>-Phenyl Isocyanide Using Chiral Palladium Catalyst

We report the polymerization of phenyl isocyanides with the chiral palladium(II) initiating system. The resulting polymers with optically active properties were obtained by polymerization of the racemic isocyanide monomer (rac-1), and enantiomerically unbalanced polymerization of the monomer was found, providing substantial evidence for the enantiomer-selective polymerization of rac-1 mediated through chiral catalyst. A comparison between the enantiomerically pure monomers, 4-isocyanobenzoyl-L-alanine decyl ester (1s) and 4-isocyanobenzoyl-D-alanine decyl ester (1r), revealed a drastic discrepancy in the reactivity ratio of their homopolymerizations. It turned out that the monomer reactivity ratio of 1s was higher than that of 1r with chiral ligands. The results clearly demonstrated the inclination for incorporation of the 1s enantiomer during the polymerization process and thus resulted in the enantiomer-selective polymerization in this system. The effects of the catalyst chirality on the optically active properties of polymerization were investigated, and it was concluded that the formation of higher-ordered conformation with a handed helicity might be attributed to the chiral induction of chiral palladium(II) catalyst. Moreover, the polymers obtained through the enantiomer-selective polymerization of the enantiomerically pure monomer were with a significant improvement of the optical activity if the chirality of the monomer and the catalyst matched with each other.     

Synthesis and mesomorphic behaviour of novel chiral nematic side chain liquid crystalline polysiloxanes

A series of novel thermotropic side chain liquid crystalline polymers was synthesized by grafting copolymerization of a mesogenic monomer, 4-allyloxybenzoyl-4′?-(4-n-alkylbenzoyl)–p-benzenediol bisate and a chiral monomer, menthyl undecylenate. The mesogenic monomers exhibited nematic threadlike textures during heating and cooling. The polymers showed thermotropic liquid crystalline properties with a broad mesomorphic region over a range of 100°C. The polymers exhibited a cholesteric mesophase with a colourful Grand-Jean texture when the content of chiral units was greater than 15?mol?%; the others exhibited nematic threadlike textures. All of the polymers were thermally stable over 300°C, and most were laevorotatory as the chiral monomer.     

Thermal,viscoelastic, and mechanical properties of DCPD-containing polymers

The thermal, viscoelastic, and mechanical properties of cured dicyclopentadiene (DCPD)-containing polymers prepared from novel DCPD-modified unsaturated epoxypolyesters and styrene were evaluated. This was accomplished using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, three-point bending test, and Brinell’s hardness. The thermal, viscoelastic, and mechanical properties of DCPD-containing polymers were strongly dependent on chemical structure. The cross-linking density (υ _e) of obtained networks increased with increasing content of carbon–carbon double bonds in the poly(ester) structure. In addition, the introduction of DCPD rings into the poly(ester) structure increased the rigidity of the molecular backbone. It resulted in obtaining polymers which showed great improvement in mechanical properties including remarkably higher storage modulus ( E_{20 ^°\textC}^￠ E_{{20\,{}^{\circ}{\text{C}}}}^{'} ), flexural modulus at bending (E _mod), hardness, lower extension at maximum force (ε-F _max), as well as higher thermal stability. These good properties make these materials highly promising as potential candidates for structural applications.     

乙烯基二联苯单体的螺旋选择性自由基聚合

为了深入理解乙烯基二联苯单体自由基聚合过程中的手性传递,进行了手性单体(+)-2-[(S)-异丁氧羰基-5-(4′-己氧基苯基)苯乙烯、非手性单体2-丁氧羰基-5-(4′-己氧基苯基)苯乙烯的均聚反应及它们二者的共聚反应,探讨了聚合温度和溶剂性质对手性单体均聚物旋光活性、手性单体含量对共聚物旋光活性以及聚合反应溶剂的超分子手性对共聚物旋光活性的影响.研究发现,降低聚合温度、采用液晶性反应介质有利于得到旋光度大的聚合物;少量手性单体的引入即可诱导共聚物形成某一方向占优的螺旋构象,比旋光度随手性单体的含量增加呈线性增长;在胆甾相液晶中制备的非手性单体聚合物不具有光学活性.这些结果表明,该类乙烯基二联苯聚合物具有动态螺旋构象,其光学活性主要依赖于主链的立构规整度和侧基不对称原子的手性.     

Aliphatic–aromatic copolyesters derived from 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol

With the massive changes taking place in the world today, the development of new thermally and mechanically stable polymeric materials is of utmost importance. This article focuses on the synthesis and thermal characterization of a new series of copolyesters that incorporate both aromatic as well as aliphatic diols. This is of interest because most polymer materials that exhibit high thermal and/or mechanical properties contain aromatic monomer units only. These aromatic units usually contribute to either the thermal or mechanical properties but typically not both. An example of this is bisphenol A polycarbonate, which has high mechanical properties but only moderate thermal properties when compared, for example, to polyimides. In recent years there has been an interest in copolyesters that contain 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol (CBDO). This aliphatic monomer imparts some very unique thermal as well as mechanical properties. This article will report the thermal properties of a new series of CBDO‐based copolyesters. These polymers include CBDO, a series of bisphenols, and terephthaloyl chloride. The series of bisphenols discussed here include bisphenol A, AF, F, and HPF. These polymers display glass transition temperatures near 200 °C and decomposition temperatures from 390–420 °C (Argon) and from 385–410 °C (Air). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3473–3478, 2004     

Soluble,thermally stable,flame retardant quinoline-based poly(ester amide)s

A new diamine was prepared via reaction between 8-hydroxy-5-nitroquinoline and 4-nitrobenzoyl chloride, followed by reduction of the nitro groups of the resulted compound. Novel quinoline-based poly(ester-amide)s were produced through polycondensation reactions of the prepared diamine with different diacid chlorides. The monomer and poly(ester-amide)s were characterized and properties of the polymers including solution viscosity, thermal behavior and stability, solubility, and crystallinity were studied.

High thermal stability and improved solubility was observed for the polymers, indicating successful designing of monomer and related polymers for overcoming the main issue of thermally stable polymers, i.e. the problem of increasing solubility versus high thermal stability.

Also, by changing the diacid chlorides for the preparation of poly(ester-amide)s, the structure-property relations were investigated.     

Synthesis of 2-phenoxy-2-phenylethyl acrylate and copolymerization with 2-phenylethyl acrylate: Estimation of monomer reactivity ratios,thermal and optical properties

A new aromatic based monomer 2-phenoxy-2-phenylethyl acrylate (PPEA) was synthesized. Copolymers of PPEA with 2-phenylethyl acrylate (PEA) were prepared by free radical polymerization. The reactivity ratios were estimated using various graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. Optical properties of polymers such as refractive indices and UV-Visible absorption were investigated. The glass transition temperature and thermal degradation behavior of the copolymers were studied. Combined with the RI, transparency and thermal properties, prepared copolymers hold great promise as materials for intraocular lens applications.     

PEGDA‐based luminescent polymers prepared by frontal polymerization

Frontal polymerization (FP) of poly(ethylene glycol) diacrylate (PEGDA) was carried out using benzoyl peroxide (BPO) as radical initiator. In addition, a pyrene containing monomer, 1‐pyrenebutyl acrylate (PyBuAc), was incorporated as a fluorescent probe in order to obtain luminescent materials with different chromophore contents. The resulting polymers were characterized by FT‐IR spectroscopy in the solid state and their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, the optical properties of these materials were studied by absorption and fluorescence spectroscopy. The maximum amount of the incorporated pyrene‐containing monomer into the polymer matrix was limited to 1 wt % by the polymerization process. The obtained labeled polymers poly(PEGDA‐co‐PyBuAc) exhibited a broad absorption band at 345 nm. The fluorescence spectra of these polymers exhibited mainly “monomer emission” so that no excimer emission was observed. It is possible to tune the color of the emitted light by varying the pyrene content in the samples. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2890–2897     

Poly(urethane‐co‐benzoxazine)s via reaction of phenol terminated urethane prepolymers and benzoxazine monomer and investigation of their properties

In the present work, a new method was developed for the combination of polyurethanes (PUs) and polybenzoxazine (PBz) to obtain novel thermoset poly(urethane‐co‐benzoxazine)s with good thermal, mechanical, and electrical properties as well as low temperature curing profile. Knowing the catalytic effect of compounds possessing free phenolic groups on ring opening polymerization of benzoxazine monomers, preparation of phenol terminated urethane oligomers (PTPU) as the macroinitiator for a benzoxazine monomer (Ba) was considered. Firstly, NCO‐terminated urethane prepolymers were prepared from the reaction of poly(tetramethyleneether glycol), and 2,4‐tolylene diisocyanate, and then end functionalized with bisphenol‐A under proper condition. DSC, DMTA, and gel content measurements were applied to find optimum ring opening polymerization condition (170°C for 1 hr and 200°C for 15 min). Various kinds of thermoset polymers were prepared by the reaction of PTPU at different molecular weights with variable contents of Ba. All of monomeric and polymeric materials were characterized by conventional spectroscopic methods and their thermal, mechanical, viscoelastic, and electrical properties were measured and properties were correlated to their structure. Due to the interesting properties of these new materials, the possibility of using them as electrical insulators with higher service temperature in comparison to common PUs were examined and their potential applicability was confirmed. Copyright © 2010 John Wiley & Sons, Ltd.     

Chiral oxazoline substituted optically active poly(m‐phenylene)s: Synthesis and coupling polymerizations of (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl) oxazoline using transition metal catalysts

Optically active poly(m‐phenylene)s substituted with chiral oxazoline derivatives have been synthesized by the nickel‐catalyzed Yamamoto coupling reaction of optically active (S)‐4‐benzyl‐2‐(3,5‐dihalidephenyl)oxazoline derivatives (X = Br or I). The structures and chiroptical properties of the polymers were characterized by spectroscopic methods and thermal gravimetric analyses. The polymers showed higher absolute optical specific rotation values than their corresponding monomer, and showed a Cotton effect at transition region of conjugated main chain. The optical activities of the polymers should be attributed to the higher order structure such as helical conformations. Moreover, the helical conformation could be induced by addition of metal salts into polymer solutions. The polymers showed good thermal stabilities, which was attributable to the oxazoline side chains. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Side-chain cholesteric liquid-crystalline elastomers containing azobenzene derivative as cross-linking agent – synthesis and characterisation

The cholesteric polysiloxanes (PLQ series) were obtained by reacting cholesteric monomer and phenolic hydroxyl monomer in different ratios with polysiloxanes. The chiral azo-containing polysiloxanes liquid-crystalline elastomers (LCEs) were synthesised by esterifying PLQ series with acyl acid of azo diacid catalysed by 4-dimethylaminopyridine (DMAP). The chemical structures and mesomorphic properties of monomers and polymers were confirmed by conventional spectroscopic methods. The elastomers displayed elastic properties, reversible phase transition and high thermal stability. The T_g values changed irregularly and T_i values decreased at the beginning and then increased afterwards. The chiral azo-LCEs showed colourful textures and a Grandjean texture could be observed, which exhibited a red shift with increasing content of azo moiety. PLQ₂–PLQ₆ exhibited selective reflection in the visible light region, but PLZ₁–PLZ₄ can only observe selective reflection when appropriate mechanical pressure was imposed on the polymers. The PLZ series was carefully investigated by ultra violet–visible spectroscopy.     

Luminescent lanthanide-containing chiral liquid crystalline polymers in the side chain

Luminescent lanthanide-containing chiral liquid crystalline polymers are graft-copolymerised using poly(methylhydrogeno)siloxane (PMHS), crosslinking agent, liquid crystalline monomer and lanthanide complexes. The chemical structures of the monomers are characterised by FTIR, ^1?H NMR and elemental analyses. The mesomorphic properties and phase behaviour are investigated by differential scanning calorimetry, thermogravimetric analysis, polarising optical microscopy and X-ray diffraction. The polymers containing less than 9 mol% of the crosslinking units reveal reversible mesomorphic phase transition, wide mesophase temperature ranges and high thermal stability. With the introduction of lanthanide complex units, the polymers are enabled with the significant luminescent properties. The temperature dependence of fluorescence intensity was studied in the liquid crystalline phase. The IR imaging shows that the lanthanide complex units evenly distribute in polymers.     

Enantiomer-selective Living Polymerization of rac-Phenyl Isocyanide Using Chiral Palladium Catalyst

We report the polymerization of phenyl isocyanides with the chiral palladium(II) initiating system. The resulting polymers with optically active properties were obtained by polymerization of the racemic isocyanide monomer(rac-1), and enantiomerically unbalanced polymerization of the monomer was found, providing substantial evidence for the enantiomer-selective polymerization of rac-1 mediated through chiral catalyst. A comparison between the enantiomerically pure monomers, 4-isocyanobenzoyl-L-alanine decyl ester(1 s) and 4-isocyanobenzoyl-D-alanine decyl ester(1 r), revealed a drastic discrepancy in the reactivity ratio of their homopolymerizations.It turned out that the monomer reactivity ratio of 1 s was higher than that of 1 r with chiral ligands. The results clearly demonstrated the inclination for incorporation of the 1 s enantiomer during the polymerization process and thus resulted in the enantiomer-selective polymerization in this system. The effects of the catalyst chirality on the optically active properties of polymerization were investigated,and it was concluded that the formation of higher-ordered conformation with a handed helicity might be attributed to the chiral induction of chiral palladium(II) catalyst. Moreover, the polymers obtained through the enantiomer-selective polymerization of the enantiomerically pure monomer were with a significant improvement of the optical activity if the chirality of the monomer and the catalyst matched with each other.     

Synthesis and properties of poly(silylenephenylenevinylene)s

Polymerization of o-, m-, and p-(dimethylsilyl)phenylacetylene by chloroplatinic acid-catalyzed hydrosilylation gave the corresponding poly(dimethylsilylenephenylenevinylene)s. The monomer reactivity and polymer structure were very much dependent upon the substituent position. Interesting optical behavior and thermal properties were observed which suggested the polymers to be useful as preceramic materials. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2263–2273, 1999     

Flame retardance and shrinkage reduction of polystyrene modified with acrylate-containing phosphorus and crosslinkable spiro-orthoester moieties

Styrene was radically copolymerized with a spiro-orthoester with an acrylate group (SOE-AC), and terpolymerized with SOE-AC and diethyl(methacryloyloxymethyl)phosphonate (DEMMP). This was done for several different feed ratios, to obtain polymers with spiro-orthoester moieties in the side chain. These polymers were then crosslinked with ytterbium triflate, as cationic initiator, via the double ring-opening polymerization. The thermal stability and fire retardant properties of these materials were evaluated by TGA and LOI. The DEMMP-containing polymers give materials which were significantly more flame retardant than the nonphosphorus-containing materials, as indicated by the LOI measurements. The volume changes measured upon crosslinking of the polymers were evaluated by density measurements with a gas pycnometer. In all the cases, expansion was observed. This indicates that SOE-AC is an effective monomer for crosslinkable polymers without volume changes.     

Synthesis of a nano‐sized chiral imprinted polymer and its use as an (S)‐atenolol carrier in the bulk liquid membrane

In this work, nanosized chiral imprinted polymers containing (S)‐atenolol ((S)‐ATN) selective sites were synthesized by using suspension polymerization in silicon oil. (S)‐ATN, methacrylic acid, and ethylene glycol dimethacrylate were used as enantiomerically pure template, functional monomer, and cross‐linker, respectively. The prepared chiral imprinted polymers were used as the carrier elements in a bulk liquid membrane (BLM). (S)‐ATN transport capability of the chiral imprinted polymers was compared with that of the nonimprinted polymer. It was shown that chiral imprinted polymers could transport (S)‐ATN through the BLM more effectively than (R)‐ATN, whereas no difference in the facilitated transport was observed between (R)‐ATN and (S)‐ATN when using nonimprinted polymer particles as the carrier element in the BLM. A kinetic model was proposed for the transportation of (S)‐ATN through the chiral imprinted polymers based BLM. It was found that the extraction of ATN from the source to the membrane controls the chiral separation process. It was also found that the pH of source and receiving phases as well as the racemic ATN concentration in source phase had very crucial effect on the chiral separation efficiency.     

Eco-friendly fast synthesis and thermal degradation of optically active polyamides under microwave accelerating conditions

<正>An optically active bulky aromatic diacid chiral monomer,(2S)-4-[(4-methyl-2-phthalimidylpentanoyl-amino) benzoylamino]isophthalic acid(1),containing a rigid phthalimide and flexible L-leucine pendent group was synthesized in five steps.A fast and clean method for direct polyamidation reaction of monomer 1 with various aromatic diamines under microwave irradiation and conventional heating was performed.The polymerization reactions provided optically active polyamides with high yields and inherent viscosities in the range of 0.36-0.74 dL/g.Their thermal properties were evaluated by thermogravimetric analysis(TGA) and differential scanning calorimetry.TGA thermograms show that the polymers are thermally stable,10%weight loss temperatures are in excess of 385℃,and char yields at 800℃are higher than 56%.The data obtained from TGA were used to study the kinetics of thermal decomposition of the resulting polymers. The interpretation of kinetic parameters(E,ΔH,ΔS andΔG) of thermal decomposition stages was evaluated using Coats and Redfern equation.