Synthesis and Characterization of Novel AB and ABA Rod–Coil Block Copolymers

Two series of novel rod–coil block copolymers, poly(ɛ-caprolactone)-b-poly{2,5-bis[(4-methoxyphenyl) oxycarbonyl] styrene} (PCL-b-PMPCS) and poly{2,5-bis[(4-methoxyphenyl) oxycarbonyl] styrene}-b-poly(ɛ-caprolactone)-b-poly{2,5-bis[(4-methoxyphenyl) oxycarbonyl] styrene} (PMPCS-b-PCL-b-PMPCS), were successfully synthesized via atom transfer radical polymerization in chlorobenzene solution using macro-initiator and CuBr/Sparteine complex as catalyst. The results show that the number average molecular weight M_n increased versus the monomer conversion and that the polydispersity M_w/M_n was quite narrow (<1.35), which were the character of controlled polymerization. The structure of the block copolymers was experimentally confirmed by ¹H NMR. And the liquid crystalline behavior of them was studied using DSC and POM. The data obtained implied that the block copolymers with low molar percentage of PMPCS block could show T_m of PCL. While only the copolymers with long rigid segment PMPCS could form liquid crystalline phase, which was quite stable with a high clearing point.     

Nitroxide‐mediated ‘living’ free radical synthesis of novel rod–coil diblock copolymers with polystyrene and mesogen‐jacketed liquid‐crystal polymer segments

The synthesis of rod–coil diblock copolymers with narrow polydispersity was achieved for the first time by TEMPO‐mediated ‘living’ free radical polymerization of styrene and 2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene. The block architecture of the two diblock copolymers thus prepared, MPCS‐block‐St (5400/2400) and MPCS‐block‐St (10 800/8700), was confirmed by GPC, ¹H and ¹³C NMR and DSC studies. The liquid‐crystalline behaviour of the copolymers was studied by DSC and polarized optical microscope. It was observed that both copolymers showed two distinct glass transitions, corresponding to polystyrene and poly(‐2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene). Above the glass transition temperature of rigid block, liquid‐crystalline phase was formed. The clearing point of the phase is higher than the polymer decomposition temperature. © 2000 Society of Chemical Industry     

Influence of alkoxy tail length on the phase behaviour of mesogen-jacketed liquid crystalline polymers with fan-shaped pendants

A series of new monomers of 2, 5-bis [(3, 4, 5-trialkoxy benzyl) oxycarbonyl] styrene (denoted as M-tri-OC_mH_2m + 1, m = 1, 2, 4, 6, 8, 10, 12, where m indicated the number of carbon atoms in the alkoxy group) were designed and synthesized. Then, their corresponding polymers P-tri-OC_mH_2m + 1 (m = 1, 2, 4, 6, 8, 10, 12) were synthesized by free radical polymerization. The chemical structure of the monomers was confirmed by elemental analysis, ¹H NMR and ¹³C NMR. The molecular characterization of polymers was performed with ¹H NMR, gel permeation chromatography (GPC). The thermal stability of polymers was investigated by thermogravimetric analysis (TGA). The phase structure and transition behaviours were studied using differential scanning calorimetry (DSC), polarized light microscopy (PLM), one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction (WAXD). We found that P-tri-OC_mH_2m + 1 (m = 1, 2) with short n-alkoxy substituents as the tail form columnar nematic (Φ_N) phase; that with the increasing length of alkoxy tails, P-tri-OC_mH_2m + 1 (m = 4, 6, 8) can demonstrate the hexagonal columnar (Φ_H) phase; however, when the length of alkoxy tails exceeded a threshold, P-tri-OC_mH_2m + 1 (m = 10, 12) only develop into columnar nematic (Φ_N) phase instead of Φ_H phase.     

Synthesis and characterization of side‐chain liquid‐crystalline polyacrylates containing azobenzene moieties

Syntheses of novel liquid‐crystalline polymers containing azobenzene moieties were performed by a convenient route with an acrylate backbone. The azobenzenes were key intermediates of the monomers, and side‐chain liquid‐crystalline polymers were prepared, that is, poly[α‐{4‐[(4‐acetylphenyl)azo]phenoxy}alkyloxy]acrylates, for which the spacer length was 3 or 11 methylene units. In addition, poly[3‐{4‐[(3,5‐dimethylphenyl)azo]phenoxy}propyloxy]acrylate was prepared with a spacer length of 3 methylene units. The structures of the precursors, monomers, and polymers were characterized with Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR techniques. The polymers were obtained by conventional free‐radical polymerization with 2,2′‐azobisisobutyronitrile as an initiator. The phase‐transition temperatures of the polymers were studied with differential scanning calorimetry, and the phase structures were evaluated with a polarizing optical microscopy technique. The results showed that two of the monomers and their corresponding polymers exhibited nematic liquid‐crystalline behavior, and one of the monomers and its corresponding polymer showed smectic liquid‐crystalline behavior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2653–2661, 2002     

Synthesis and properties of side‐chain liquid‐crystalline polysiloxanes containing hemiphasmidic mesogens

The synthesis of hemiphasmidic monomers 4‐[(3,4,5‐triethoxy)benzoyloxy]‐4′‐[(p‐allyloxy)benzoyloxy]biphenyl (M₁), 4‐[(3,5‐diethoxy)benzoyloxy]‐4′‐[(p‐allyloxy)‐benzoyloxy]biphenyl (M₂), and of the corresponding side‐chain liquid‐crystalline polysiloxanes (P₁, P₂) was carried out. For comparison, rodlike monomer 4‐[(p‐ethoxy)‐benzoyloxy]‐4′‐[(p‐allyloxy)benzoyloxy]biphenyl (M₃) and its polysiloxanes (P₃) were also prepared. The chemical structures of the monomers and polymers obtained were confirmed by FTIR and ¹H‐NMR spectra. Their mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. The relationship between structures and properties was discussed. It was observed that M₁ and M₃ were enantiotropic nematic phase, M₂ was monotropic mesophase, and their poly(methylsiloxanes) (P₁–P₃) possessed a broad range enantiotropic nematic phases and high thermal stability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 946–952, 2005     

Effects of molecular weight on liquid-crystalline behavior of a mesogen-jacketed liquid crystal polymer synthesized by atom transfer radical polymerization

The synthesis of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) with different molecular weight and low polydispersity was achieved by atom transfer radical polymerization in methoxybenzene solution using 1-bromoethylbenzene as an initiator and CuBr/sparteine complex as a catalyst. The concentration of the living centers throughout the polymerization was found to be constant. The liquid-crystalline behavior of the polymers with M_n ranging from 3800 to 17,400 g/mol was studied using DSC and POM. Only the polymers with M_n beyond 10,200 g/mol formed a liquid-crystalline phase, which was quite stable with a high clearing point (higher than the decomposition temperature of the polymer).     

Synthesis and properties of polyacetylenes having pendent phenylethynylcarbazolyl groups

Novel acetylene monomers substituted with phenylethynylcarbazolyl groups, 3-[(4-octylphenyl)ethynyl]-9-propargylcarbazole (1), 3,6-bis[(4-octylphenyl)ethynyl]-9-propargylcarbazole (2), 9-(4-ethynylphenyl)-3-[(4-octylphenyl)ethynyl]carbazole (3), and 9-(4-ethynylphenyl)-3,6-bis[(4-octylphenyl)ethynyl]carbazole (4) were synthesized, and polymerized with Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃] and WCl₆-n-Bu₄Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 9200 to 94?000 were obtained in 20-98% yields. The IR spectra of the polymers revealed that acetylene polymerization took place at the terminal ethynyl group, while the ethynylene group remained intact. The UV-vis absorption band edge wavelengths of W-based poly(3) and poly(4) were longer than those of the other polymers. W-Based poly(4) emitted fluorescence with the highest quantum yield (41%). Poly(1) exhibited excimer-based fluorescence in dilute solution.     

Synthesis and characterization of diblock copolymers based on crystallizable poly(ε-caprolactone) and mesogen-jacketed liquid crystalline polymer block

Diblock copolymers comprising crystallizable poly(ε-caprolactone) and poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) were synthesized by ring-opening polymerization of ε-caprolactone and subsequent atom transfer radical polymerization (ATRP) of MPCS. The molecular structure of the copolymers was confirmed by ¹H NMR spectroscopy and GPC. Kinetic study of ATRP showed that the polymerization proceeded in a controlled way up to high conversions. Three series of diblock copolymers were obtained with relatively narrow polydispersity indices (PDI≤1.11) and PCL blocks of 8000, 12,900, and 22,800 molecular weights, respectively. The existence of microphase separation was identified by differential scanning calorimetry (DSC) and directly observed through transmission electron microscopy (TEM). The melting behavior of PCL block was significantly affected by the length of PCL block and composition of PMPCS. The thermotropic liquid crystalline behavior was examined by polarized optical microscopy (POM) and DSC. The result showed that the diblock copolymer exhibited liquid crystalline behavior when the degree of polymerization (DP) of PMPCS block was not less than 44.     

Synthesis and mesomorphic behavior of terminally carboxyl oligo(ethylene oxide) monomethyl ethers-substituted side chain liquid crystalline polysiloxanes. I

A series of alkene monomers containing carboxyl biphenyl benzoate ester or carboxyl p,p′-phenyl benzoate ester based on mesogenic core with a carboxyl (±)-2-methyl ethylene glycol monomethyl ether group or various lengths of carboxyl oligo (ethylene oxide) monomethyl ethers as the terminal group were synthesized. And they were grafted onto the poly(methylhydrosiloxanes) (PMHS) by the platinum catalyzed hydrosilylation process. Their molecular structure, the thermal transitions temperature, and mesophase texture of monomers and of polymers were characterized using ¹H nuclear magnetic resonance, differential scanning calorimetry, and polarizing optical microscopy with hot stage. The polymers obtained all show smectic phase while their precursor monomers show both smectic and/or nematic phase, or in some cases, no mesophase. The factors governing mesophase texture and transition temperature are discussed. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of side‐chain cholesteric liquid‐crystalline polysiloxanes containing different space groups

A series of liquid‐crystalline (LC) polysiloxanes were synthesized by two different cholesteric monomers, cholest‐5‐en‐3‐ol(3β)‐10‐undecenoate and cholesteryloxycarbonylmethyl 4‐allyloxybenzoate. The chemical structures and LC properties of the monomers and polymers were characterized by various experimental techniques, including Fourier transform infrared spectroscopy, ¹H‐NMR, elemental analysis, differential scanning calorimetry, and polarized optical microscopy. The specific rotation absolute values increased with increasing rigid spacers between the main chain and the mesogens. All of the polymers exhibited thermotropic LC properties and revealed cholesteric phases with very wide mesophase temperature ranges. With a reduction in the soft‐space groups in the series of polymers, the glass‐transition temperature and the isotropic temperature increased slightly on heating cycles. Reflection spectra of the cholesteric mesophase of the series of polymers showed that the reflected wavelength shifted to short wavelengths with decreasing soft‐space groups in the polymers systems, which suggested that the helical pitch became shorter with increasing rigid‐space groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel thermotropic liquid crystalline polyphosphonates

Main chain liquid crystalline polyphosphonates containing semi-flexible phenylester mesogen with even number of methylene spacers (2-10) have been synthesized. The monomers and polymers were characterized by IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The spectral details are in accordance with the structures. All the polymers were exhibited liquid crystalline property in the Hot stage optical polarized microscope (HOPM). DSC thermal analysis confirms the mesophase formation for all the polymers. The grain size of the liquid crystalline mesophase is increasing with increasing methylene chain. T_g, T_m and T_i of the polymers decreased with increase in spacer length. The T_g of these phosphorus-containing polymers is much lower than that of non-phosphorus polymers containing triad ester mesogens. Energy minimized structures for the molecules which mimic the polymer chain suggests that the reduction in T_g may be due to entanglement raised by incorporation of phosphorus heterogeneity.     

Synthesis,structure, and phase behavior of new chiral liquid‐crystalline polysiloxanes based on mesogenic menthyl monomers

Six new chiral monomers ( M ₁ – M ₆ ), and their corresponding side chain polymers ( P ₁ – P ₆ ) containing menthyl groups were synthesized. The chemical structures of M ₁ – M ₆ were characterized with FTIR and ¹H NMR. The structure–property relationships of the monomers and polymers obtained are discussed. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X‐ray diffraction measurements. Some compounds containing menthyl groups formed mesophase when a flexible spacer was inserted between the mesogenic core and the menthyl groups by reducing the steric hindered effect. The monomers M ₁ , M ₄ , and M ₅ did not reveal mesomorphic properties because of the weaker rigid core or the longer flexible terminal groups, whereas M ₂ , M ₃ , and M ₆ all revealed cholesteric phase. Except P ₄ and P ₅ , the homopolymers P ₁ – P ₃ and P ₆ showed a smectic A phase. In addition, melting, glass transition temperature, or clearing temperature increased, and the mesophase temperature range widened with increasing the rigidity of mesogenic core or decreasing the length of the flexible spacer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

New thermochromic liquid–crystalline polymer: Synthesis and phase behavior

A series of new thermochromic side‐chain liquid–crystalline polymers were prepared. The chemical structures of the resulting monomers and polymers were characterized by element analyses, FTIR, ¹H‐NMR, and ¹³C‐NMR. Their mesogenic properties were investigated by differential scanning calorimetry, thermogravimetric analyses, polarizing optical microscopy, and X‐ray diffraction measurements. The influence of the content of dye groups on phase behavior of the polymers was discussed. The polymers P₁–P₃ showed smectic phase, and P₄–P₇ revealed cholesteric phase. The polymers containing less than 30 mol % of the dye groups showed good solubility, reversible phase transition, wider mesophase temperature ranges, and higher thermal stability. Experimental results demonstrated that the clearing temperature and mesophase temperature ranges decreased with increasing the concentration of the dye groups. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 329–335, 2005     

Zur Synthese und Funktionalisierung neuer Poly[(silylen)‐2,5‐thiophene]

Treatment of 2,5‐dilithiothiophene with (dimethylamino) methylsilylbis(triflates) gave poly[(dimethylamino‐silylene)‐2,5‐thiophene] 4 in high yield. The amino–silyl bond was cleaved selectively by triflic acid leading to triflate substituted poly[(silylene)‐2,5‐thiophene] 5 . Conversions of this polymers with nucleophiles gave other functionalized derivatives 6 – 9 . Hydrosilylation reaction between silicon–vinyl and silicon–hydrogen derivatives results in polymer networks which may serve as interesting preceramic materials. The structures of the polymers were proven by NMR spectroscopy (²⁹Si, ¹³C, ¹H).     

Structure-property relationship of thermotropic liquid-crystalline vinyl polymers containing no traditional mesogen

A series of non-mesogenic vinyl monomers, 2,5-bis(alkoxycarbonyl)styrene, were synthesized and polymerized via free radical polymerization. The alkoxy groups were systematically varied to investigate the effects of their size and architecture on the thermotropic liquid-crystalline properties of the resultant polymers. Although no traditional mesogen was present in the macromolecular structure, all the polymers revealed stable hexagonal columnar liquid-crystalline phase at the temperatures well above their glass transitions when the molecular weights were high enough, as evidenced by a combinatory analysis of differential scanning calorimetry, polarized light microscopy, and one- and two-dimensional wide-angle X-ray diffraction techniques. For the polymers containing five carbon atoms in the alkoxy terminals, the temperatures of glass transition and mesophase formation decreased and the d-spacing value of mesophase increased as the methyl substituent moved away from the connecting phenyl ring. Increasing the number of methyl group or the size of the substituent had the same effect. In the case of polymers with Y-shaped alkoxy terminals, the larger the side groups, the lower the glass-transition temperature and mesophase formation temperature and the larger the d-spacing value of mesomorphic structure.     

New polymer syntheses. Part 7. New unsaturated polyurethanes: synthesis and characterization†

A novel series of polyurethanes was prepared via step-growth solution polymerization, by reaction of arylidene monomers, e g 2,5 bis(4-hydroxybenzylidene)cyclopentanone ( I ), 2,5-divanillylidenecyclopentanone ( II ), 2,6-bis(4-hydroxybenzylidene)cyclohexanone ( III ), 2,6-divanillylidenecyclohexanone ( IV ) or 2,7-bis(4-hydroxybenzylidene)cycloheptanone ( V ) with diisocyanates such as toluylene diisocyanate and methylene bis(4-phenylisocyanate). To characterize these polymers, the corresponding model compounds were prepared from monomers I–V and phenylisocyanate. The polymers were characterized by reduced viscosity measurements, IR spectroscopy, ¹H NMR, solubility and determination of their crystallinity. Characterization of the model compounds was accomplished by elemental analysis, IR and ¹H NMR spectroscopy. The thermal stabilities of the polymers were evaluated by thermogravimetric analysis. The morphology of one of these polymers was examined by scanning electron microscopy. © 1999 Society of Chemical Industry     

Synthesis,characterization, and mesomorphic behavior of side-chain liquid crystalline copolysiloxane polymers I. with an oligo (ethylene oxide) unit and a cyano unit in the side chain

The syntheses and characterizations of poly [4-allyloxy-benzoic acid [4-(2-methoxy) ethoxy] biphenyl]-4-yl ester-co-4-allyloxy-[(4-cyano)-4-phenyl] carboxyl benzoate ester (poly [(MS3BDBE1)-co-(MCN)]_x/y) (where x/y represents the molar ratio of the two structural units on the side chain) were performed in this study. The molar compositions of the structural units on the copolymers side chain were characterized by¹H NMR. The transition temperatures, mesophase texture, and layer spacing (dl) of the polysiloxane polymers and copolymers were determined by differential scanning calorimetry (DSC), polarized optical microscopy, and X-ray diffraction patterns. The effects of the molar composition in the copolymers on the mesophase texture, transition temperatures, enthalpy/entropy change of mesophase/isotropic transition, dl of these copolymers were also discussed.     

线型聚苯乙烯支载手性噁唑烷酮的合成及其性能研究

噁唑烷酮手性单体与苯乙烯经溶液聚合得到线型聚苯乙烯支载的(4s)-4-苄基-噁唑-2-烷酮手性助剂,经IR,NMR分析证实了其结构,DSC及TGA分析表明该聚合物具有较好的稳定性,考察了单体浓度对聚合物性能的影响。     

Oxidative Hydrophenylation of Ethylene Using a Cationic Ru(II) Catalyst: Styrene Production with Ethylene as the Oxidant

The complex [(MeOTTM)Ru(P(OCH₂)₃CEt)(NCMe)Ph][BAr′₄] (MeOTMM=4,4’,4’’-(methoxymethanetriyl)-tris(1-benzyl-1H-1,2,3-triazole), BAr′₄=tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) is used to catalyze the hydrophenylation of ethylene to produce styrene and ethylbenzene. The selectivity of styrene versus ethylbenzene varies as a function of ethylene pressure, and replacing the MeOTTM ligand with tris(1-phenyl-1H-1,2,3-triazol-4-yl)methanol reduces the selectivity toward styrene. For styrene production ethylene serves as the oxidant to produce ethane, as determined by both ¹H NMR spectroscopy and GC-MS. The Ru(III/II) potentials of [(MeOTTM)Ru[P(OCH₂)₃CEt](NCMe)Ph][BAr′₄] (0.86 V) and [(HC(pz⁵)₃)Ru[P(OCH₂)₃CEt](NCMe)Ph][BAr′₄] (0.82 V) (HC(pz⁵)₃=tris(5-methyl-pyrazolyl)methane) are nearly identical. Since catalytic conversion of ethylene and benzene by [(HC(pz⁵)₃)Ru[P(OCH₂)₃CEt](NCMe)Ph][BAr′₄] is known to selectively produce ethylbenzene, the formation of styrene using [(MeOTTM)Ru[P(OCH₂)₃CEt](NCMe)Ph][BAr′₄] is attributed to the substituents on the triazole rings of the MeOTTM ligand.     

Synthesis,properties, and self‐assembly of poly(benzyl ether)‐b‐polystyrene dendritic–linear polymers

Poly(benzyl ether)‐b‐polystyrene dendritic–linear polymers were successfully synthesized using a dendritic chloric poly(benzyl ether) (G₁‐Cl, G₂‐Cl, and G₃‐Cl) as the macroinitiator through the atom transfer radical polymerization process. The structure and properties of the resultant polymers were characterizated by gel permeation chromatography, ¹H‐NMR, Fourier transform IR, thermogravimetric analysis, and differential scanning calorimetry. It was found that the temperature, reaction time, molar ratio of the macroinitiator to styrene, and the generation number of the macroinitiator have significant effects on the molecular weights, conversion, and polydispersities of the resulting polymers. These dendritic–linear block polymers had very good solubility in common organic solvents at room temperature. The terminal group (dendritic segments) of the polymers can affect their thermal stability. These dendritic–linear polymers after self‐assembling in selective solvents (chloroform/acetone) formed core–shell micelles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1106–1112, 2005