Characteristic ratio of poly(tetrahydrofurfuryl acrylate) and poly(2-ethylbutyl acrylate)

The synthesis, characteristic ratio C_∞ and glass transition temperature (T_g) of poly(tetrahydrofurfuryl acrylate) (PTHFA) and of poly(2-ethylbutyl acrylate) (P2EBA) are reported. P2EBA has slightly lower flexibility (C_∞ = 9.2) than PTHFA (C_∞ = 8.6), mainly because of the higher bulkiness of its side group and the closer proximity to the main chain. The C_∞ results compared with the corresponding polymethacrylates show an increase in flexibility due to the absence of the α-methyl group. Comparison with poly(methyl acrylate) clearly shows the influence of the bulkiness of the side group on the chain flexibility. The lower T_g of P2EBA than that of PTHFA may be explained by the higher flexibility of the 2-ethylbutyl side group. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1589–1592, 1997     

疏水相互作用引起Gemini表面活性剂柔性联接链的弯曲

为了理解gemini表面活性剂柔性烷基联接链在自组织过程中的特殊作用,我们合成了三种gemini表面活性剂烷基-a,w-二（二-十二烷基甲基溴化铵）（记为2C12-s-2C12×2Br (s=3, 6, 8)）。2C12-s-2C12×2Br在水表面构成铺展膜后,由于每个分子带有4根烷烃链,它们形成了稠密的烷烃尾链层。增强的烷烃尾链与联接链间的疏水相互作用促使联接链弯曲朝向空气一端,可发生弯曲的联接链长度要小于吸附在水溶液表面上的gemini表面活性剂C12-s-C12×2Br,后者每个分子只有2根烷烃链。由此可见,增强的烷烃尾链与联接链间的疏水相互作用可以有效地促进联接链的弯曲。     

Cholesterol-based dimeric liquid crystals: synthesis and mesomorphic behaviour

Chiral non-symmetric dimeric liquid crystals consisting of a cholesteryl ester moiety as chiral entity and a biphenyl aromatic core, interconnected through n-butyl (C₄) or n-pentyl (C₅) parity alkylene spacers, have been synthesized and investigated for their liquid crystalline properties. All the dimers exhibit enantiotropic mesophases. The first member of the dimers having the C₄ central spacer exhibit only the chiral nematic (N*) mesophase, while the higher homologues also show smectic A (SmA) and twist grain boundary (TGB) mesophases. The dimers of the other series containing the C₅ central spacer also have stable SmA, TGB and N* mesophases, except for the first which does not show the TGB phase. Both series of compounds show a weak odd-even effect with terminal alkyl chain substitution, while the spacer length has a marked influence on the phase transition temperatures.     

Influence of chemical structure on the optical properties of new side-chain polymers containing cholesterol

Poly[1-(cholesteryloxyhexyloxy)ethylene] (PHET) and poly[1-(cholesteryloxycarbonyl-hexyloxy)ethylene] (PHES) were prepared by reacting poly(vinyl alcohol) with cholesteryloxyhexyloxy bromides (CHB) or cholesteryloxycarbonylhexyloxy bromides (CEHB), and their thermal and optical properties were investigated. PHET and PHES exhibited monotropic cholesteric phases; however, their thermal behaviours depended on the cholesteryl groups and alkylene spacers with different chemical structures. PHET did not display reflection colours over its entire cholesteric range, whereas PHES did display reflection colours. These results suggested that the thermal stability and helical twisting power (HTP) of these polymers strongly depend on the difference in the chemical structures of the flexible spacer via cholesterol. The mesophase properties of PHET and PHES differed substantially from those of poly(cholesteryl-ω-acryloyloxyalkanoates). The results indicate that the mode of chemical linkage between the side-chain group and the main chain as well as that between the alkylene spacer and side chain play important roles in determining the thermal stability, mesophorphic structure and HTP of the cholesteric mesophases.     

Organometallic chiral liquid crystals: bis{4-[ω-(cholest-5-en-3-yloxycarbonyl)alkoxy]phenylethynyl}mercury complexes

We report the synthesis and thermal behaviour of the first chiral organometallic trimesogens having bis[(4-phenyl)ethynyl]mercury as the central core connected on either side to cholesteryl ester moieties through either even-even (C₄) or odd-odd (C₃, C₅ and C₇) central alkylene spacers. All the organomercury trimesogens exhibit a chiral nematic phase. These mercury complexes are extremely sensitive to heat, in a manner reminiscent of other reports.     

Dielectric and Viscoelastic Behavior of Poly-(n-Butyl Methacrylate) Containing Cholesteric Compounds

Dielectric and dynamic mechanical behavior of poly(n-butyl methacrylate) (PBMA) containing small concentrations of cholesteryl chloride (ChCl), cholesteryl caprylate (ChCp), and cholesteryl laurate (ChL) have been studied in the temperature range -20 to 80°C. Tan αmax (dielectric and mechanical) in all systems containing an additive shifts to lower temperature compared to that in pure PBMA. In the glassy region, the dynamic storage modulus E′ for all the PBMA plus additive systems is higher than that for pure PBMA. This behavior is similar to the β-peak suppression and the increase in tensile strength of poly(vinyl chloride) on addition of a small concentration of plasticizer. Using the WLF equation with C₁ and C₂ obtained from the data on pure PBMA, the reference temperature T_o for PBMA plus additive systems are determined for the best fit of the experimental points to the WLF curve and are in agreement with measured glass-transition temperatures. With respect to T_o of pure PBMA, the T_o of PBMA plus additive systems are lowered, and the lowering due to these additives is in the order ChL < ChCp < ChCl. From spectrophotometric studies in solutions of polymer plus additives, equilibrium constants for the 1:1 and 1:2 complexes between the polymer and the additive are evaluated. The magnitude of the equilibrium constant K₁ increases in the order ChL > ChCp > ChCl, and hence it is concluded that the extent of β-peak suppression depends on the strength of polymer-additive interaction.     

Polymeric ruthenium bipyridine complexes: New potential materials for polymer solar cells

Methyl methacrylate‐containing bipyridine monomers were synthesized with a hydoxy‐functionalized bipyridine. The 4′‐methyl group of the 2,2′‐bipyridine was used to introduce hydoxy‐functionalized alkyl spacers of two different lengths. Two, different synthetic routes were applied for the preparation of the hydoxy‐functionalized bipyridine via a bromo‐(C₇ spacer) or a silylated‐(C₃ spacer) intermediate. A copolymer of poly(methyl methacrylate) with bipyridine units in the side chains was prepared by free‐radical copolymerization and characterized with ¹H NMR, ultraviolet–visible, and IR spectroscopy as well as gel permeation chromatography. The bipyridine units of the copolymer were reacted with ruthenium bipyridine precursors. The resulting graft copolymers displayed promising photophysical and electrochemical properties, opening interesting perspectives for applications in the field of solar‐cell devices. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 374–385, 2004     

Interfacial dilational properties of anionic gemini surfactants with polymethylene spacers

The dilational properties of anionic gemini surfactants alkanediyl-α,ω-bis(m-octylphenoxy sulfonate) (C₈C_mC₈) with polymethylene spacers at the water–air and water–decane interfaces were investigated by oscillating barriers and interfacial tension relaxation methods. The influences of oscillating frequency and bulk concentration on the dilational properties were explored. The experimental results show that the linking spacer plays an important role in the interfacial dilational properties. The moduli pass through one maximum for all three gemini surfactants at both water–air and water–decane interfaces. However, the values of moduli at the water–air interface are obviously higher than those at the water–decane interface because the sublayer formed by spacer chains will be destroyed by the insertion of oil molecules. Moreover, with the increase of spacer length, the surface adsorption film becomes more viscous at high concentration, which can be attributed to the process involving the formation of the sublayer. On the other hand, the spacers of the adsorbed C₈C₆C₈ molecules will extend into the oil phase when the interface is compressed. As a result, the interfacial film becomes more elastic with the increase of spacer length at high concentration. The experimental results obtained by the interfacial tension relaxation measurements are in accord with those obtained by the oscillating barriers method.     

Salicylaldimine-based symmetric dimers: synthesis and thermal behaviour

Several symmetrical dimers comprised of salicylaldimine-moieties connected through ester linkages to the termini of odd-parity alkanediols have been synthesized and investigated for their thermal behaviour. In order to understand the structure-property relations, the lengths of the central alkylene spacers (C₃ and C₅) as well as those of the terminal alkoxy chains (C₆ to C₂₂) have been varied. The dimers with a C₃-alkylene spacer are non-liquid crystalline, while some of the compounds having a C₅-alkylene spacer exhibit liquid crystalline properties. The dimer, with a C₅-alkylene spacer and C₆-alkoxy tails, shows an intercalated smectic C (SmC_c) phase, whereas the C₈, C₁₀, C₁₁, and C₁₂ homologues are non-mesomorphic. The higher homologues of this series with C₁₆, C₁₈, C₂₀ and C₂₂ alkoxy tails show a mesophase that has the signatures of a two-dimensional banana (B₁) phase. This mesophase is enantiotropic in the C₁₆ and C₁₈ homologues while it is monotropic in the other homologues. In these dimers, the spacer length has a remarkable influence on the thermal behaviour.     

Mesogenic Unsymmetric dimers containing cholesteryl ester and tolane moieties

Among unsymmetric oligomesogens, chiral dimers formed by connecting a cholesteryl ester fragment with various aromatic mesogenic cores through a polymethylene spacer have been attracting much attention due to their remarkable thermal behaviour. In particular, dimers containing a diphenylacetylene segment having an alkoxy chain have shown interesting mesomorphic behaviour. In view of this a new series of unsymmetric dimers consisting of a diphenylacetylene moiety having an alkyl chain and a cholesteryl ester unit joined through a paraffinic spacer have been synthesized and their liquid crystalline properties characterized. The lengths of the central methylene spacer (C₃, C₄, C₅ and C₇) as well as that of the alkyl chain (n-butyl, n-pentyl, n-hexyl and n-heptyl) have been varied to establish structure–property relationships. These investigations have revealed that all the dimers exhibit smectic A, twist grain boundary and chiral neamtic (N*) phases with the exception of one of the dimers for which only the N* phase was observed. Some differences in the mesomorphic properties of the unsymmetric dimers containing odd or even parity methylene spacers have been observed. The majority of dimers having an even (C₄) parity paraffinic spacer show a blue phase while the dimers with odd (C₃, C₅ and C₇) parity spacers exhibit the chiral smectic (SmC*) phase. In some cases, the SmC* phase exists well below (?60°C) and above room temperature.     

Conformation of random polypeptide chains

The characteristic ratios C_of and C_∞ are calculated for infinitely long poly(L-amino acid) chains having a? CH₂? R′ substitution at the C^α atom, as functions of the valence angle τ at the C^α atom. The value of C_of is found to increase from 1.6 to 2.3 as τ varies from 105 to 115°. On the other hand, C_∞ decreases with increasing τ in the range 105–111°, passes through a minimum at 111°, and then increases slowly. Since, C_∞ is much less dependent on τ in the most commonly observed range (110–115°), any variation in τ in this range due to solvent would not appreciably affect C_∞. The calculated temperature coefficient of C_∞ is negative and increases significantly in absolute magnitude even for small deviations in τ from 110°.     

Liquid-crystalline polyesters based on branched propylene spacers

A new promising concept of spacer modification in main chain liquid crystalline polymers is the use of branched alkylene spacers. In this article we give as a first example the polyesters of p, p′-terphenyl-4,4′-dicarboxylic acid as mesogenic unit and disubstituted propylene spacers. The steric restrictions of the spacers lower the melting points compared with the polyesters with linear spacer but they do not flexibilize the main chains as linear alkylspacers do. This leads to a residual stability range of the liquid crystalline state in the homologues of polyesters with disubstituted spacer. The melting and clearing points are lowered to the same extent. Because of the solubility of the higher homologues in common solvents it is possible for the first time to determine molecular masses of this polymer class based on p, p′-terphenyl-4,4′-dicarboxylic acid and aliphatic diols more exactly. X-ray scattering indicates that long side chains are arranged parallel to the main chain and have no longer influence on transition temperatures and intermolecular distances. © 1996 John Wiley & Sons, Inc.     

Functionalized polymers I. Poly(dichloroalkyl itaconates), synthesis and solution properties

The synthesis of poly(di-2-chloroethyl itaconate) (PD2CEI) and poly(di-3-chloropropyl itaconate) (PD3CPI) was carried out. The dilute solution behaviour of these polymers in tetrahydrofuran and chloroform at 298 K has been studied, by viscometry, membrane osmometry, and size-exclusion chromatography (SEC) measurements. The Kuhn-Mark-Houwink-Sakurada relationships were established. The flexibility factors σ and C_∞ and the thermodynamic parameters B were calculated using the Stockmayer-Fixman equation. The results obtained are compared with those found for the corresponding poly(methacrylates) and the poly(dialkyl itaconates), and discussed in terms of specific influence of the chlorine incorporated in the side chain.     

LC-Polyimides. XIX. Chiral and thermotropic poly(esterimide)s based on N-(4′-caboxyphenyl)trimellitimide and novel chiral spacers

Starting from commercial S- or R-3-bromo-2-methylpropanol, several new spacer diols were prepared. These spacers were polycondensed with the acid chloride of N-(4′-carboxyphenyl)trimellitimide. The resulting poly(ester-imide)s were characterized by elemental analyses, viscosity measurements, ¹H-NMR spectroscopy, DSC- and WAXD-measurements and optical microscopy. The poly(ester-imide)s derived from chiral, aliphatic spacers form layer structures in the solid state, but no liquid crystalline phase. With nonsymmetrical, nonchiral semialiphatic spacers, poly(ester-imide)s were obtained, which form a smectic E or H phase in the solid state, a smectic-A or -C phase in the melt, and a nematic phase, when the spacer possesses an odd number of CH₂ groups. The polycondensation of a chiral semialiphatic spacer yielded thermotropic poly(ester-imide)s with either S- or R-configuration. WAXD patterns measured with synchrotron radiation at various temperatures proved that a layer structure exists in the solid state (smectic-E^* or H^*) and a chiral smectic-A^* or -C^* phase plus a cholesteric phase in the melt. A 1 : 1 blend of the S- and R-polyesters was also studied, but did not show unusual features. © 1995 John Wiley & Sons, Inc.     

Synthesis and thermal behaviour of salicylaldimine-based liquid crystalline symmetrical dimers

A series of symmetrical dimers consisting of salicylaldimine moieties connected by flexible alkylene central spacer via ether linkages has been synthesized. In order to validate the empirical rule suggested by Date et al. to account for the smectic behaviour of such dimers, the chain length of the terminal alkoxy chain has been kept constant (C₈) while the number of methylene units in the central spacer was varied from C₃ to C₁₁. Another aim of the present investigation was to understand structure-property relationship in these dimers in which the salicylaldimine mesogenic segment has been used for the first time in dimers. The mesomorphic behaviour of these dimers was evaluated using optical microscopy and differential scanning calorimetry and the structure of some of the mesophases has been further investigated with the help of X-ray diffraction. Our studies reveal that the dimers consisting of 3 to 8 methylene units in the flexible spacer show only smectic (smectic C and smectic A) phases. For the dimers containing 4, 6 and 8 methylene units in the central spacer, a unique filament growth pattern has been observed in the smectic A phase while cooling from the isotropic phase. The dimers containing of C₉ to C₁₁ methylene groups exhibit the nematic phase in addition to smectic modifications. This observation indicates that when the terminal chains are shorter than the spacer, the tendency to form smectic phases is not fully extinguished but is perhaps reduced.     

Simultaneous kinetic and microdielectric studies of some epoxy–amine systems

Three reactive epoxy–amine systems based on diglycidyl ether of bisphenol A (DGEBA) with 4,4′-diaminodiphenylsulfone (DDS), 4,4′-methylenebis [3-chloro 2,6-diethylaniline] (MCDEA), and 4,4′-methylenebis [2,6-diethylaniline] (MDEA), were studied during isothermal curings at 140 and 160°C. The simultaneous kinetic and dielectric studies allow to express conductivity, σ, in terms of conversion, x, and of glass transition temperature, T_g. The conductivity, σ₀, of the initial monomer mixture and, σ_∞ of the fully cured network are measured. It is found that:

• The glass transition temperature, T_g, versus conversion, x, curves follows the equation of Di Benedetto modified by Pascault and Williams
• There exists a linear relation between log σ/log σ₀ and T_g.

So, it is possible to predict both kinetic and dielectric behaviors of these epoxy-amine systems by the knowledge of T_g0, ΔC_p0, and σ₀, respectively, glass transition temperature, heat capacity, and conductivity of initial monomer mixture, T_g∞ and ΔC_p∞, and σ_∞, respectively, glass transition temperature and heat capacity and conductivity of fully cured network. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2911–2921, 1998     

Molecular design of diene monomers containing an ester functional group for the synthesis of poly(diene sulfone)s by radical alternating copolymerization with sulfur dioxide

Functional poly(diene sulfone)s are prepared by the radical alternating copolymerization of 1,3‐diene monomers containing an ester substituent with sulfur dioxide. Methyl 3,5‐hexadienoate (MH) and methyl 5,7‐octadienoate (MO) with both an alkylene spacer and a terminal diene structure are suitable to produce a high‐molecular‐weight copolymer in a high yield, while the copolymerization of 5,7‐nonadienoic acid, ethyl 2,4‐pentadienoate, and ethyl 4‐methyl‐2,4‐pentadienoate including either an alkylene spacer or a terminal diene structure lead to unsuccessful results. The ¹³C NMR chemical shift values of MH and MO suggest a high electron density at their reacting α‐carbon for exhibiting a high copolymerization reactivity. Fluorene‐containing diene monomers, 9‐fluorenyl 3,5‐hexadienoate (FH) and 9‐fluorenyl 5,7‐octadienoate (FO), are also prepared and copolymerized with sulfur dioxide. The thermal and optical properties of the poly(diene sulfone)s containing the methyl and fluorenyl ester substituents in the side chain are investigated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1000–1009     

Cyclic and linear poly(ferrocenylene alkylene)s synthesized from addition‐condensation polymerization of ferrocene with aldehydes

Oligo‐ and poly(ferrocenylene alkylene)s, [Fe(C₅H_5‐x)(C₅H_5‐y)CHR]_n (x = y = 1 or x = 2, y = 0; R = alkyl, aryl), were synthesized by Lewis acid‐promoted addition‐condensation polymerization of ferrocene with aldehydes. The reaction of alkyl aldehydes, such as n‐hept‐CHO, EtCHO and nBuCHO, with ferrocene yields a mixture of the cyclic and linear poly(ferrocenylene alkylene)s, while aryl aldehyde, such as C₆F₅CHO, CF₃C₆H₄‐4‐CHO and MeC₆H₄‐4‐CHO, forms the linear polymers exclusively. The linear polymer has terminal ? Fe(C₅H₄)(C₅H₅) and ? CH₂Aryl groups, which are characterized by high resolution mass spectroscopy. Results of addition‐condensation polymerization of ferrocenemethanol catalyzed by BF₃ indicate that the propagating polymer of the above addition‐condensation polymerization contains terminal 1‐hydroxyalkyl‐ferrocenylene group, ? Fe(C₅H₄)[C₅H₄{CH(OH)R}]. The trimer prepared from ferrocene and paraformaldehyde dimethylacetal contains 1,1′‐, 1,2‐, and 1,3‐ferrocenylene units, suggesting that the polymers obtained from alkyl and aryl aldehydes are also composed of these structural units. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3627–3635     

Properties and chain flexibility of poly(tetrahydro-4H-pyranyl-2-methacrylate)

The dilute-solution properties of six poly(tetrahydro-4H-pyranyl-2-methacrylate) (PTHPM) fractions covering the molecular weight (M _w) range 4.8 × 10⁴ to 8.4 × 10⁵ (M _w/M _n = 1.2–1.4) were studied in tetrahydrofuran, a good solvent, and in isobutanol, a θ solvent a t 30.5°C as determined by light scattering from the A₂ vs. T plot. The unperturbed dimensions were calculated from a low-angle laser light-scattering and intrinsic-viscosity data. The results indicate that PTHPM is less extended chain than poly(cyclohexyl methacrylate) (PCyM). The higher flexibility of PTHPM parallels the lower T, (57°C) of this polymer relative to PCyM (66°C).     

Synthesis,liquid crystallinity,and mechanical properties of thermotropic polyquinolines

Thermotropic liquid-crystalline polyquinolines with high molecular weights, i.e., poly[2,2′-(α,ω-dioxyphenylene (or -dioxybiphenylene) alkane)-6,6′-(4,4′-dioxybiphenyl)-bis(4-phenylquinoline)]s (P-H-B1Mns or P-H-B2Mns), were synthesized by polycondensation of 4,4′-bis(4-amino-3-benzoylphenoxy)biphenyl and α,ω-bis(4-acetophenoxy (or -acetobiphenoxy))alkanes. For P-H-B1Mn series, the T_m and T_i were in the range of 129–230°C and 156–254°C, respectively, while for the P-H-B2Mn series, those were 182–275°C and 217–309°C, respectively. The introduction of both the dioxybiphenylene group and an alkylene spacer induced thermotropic liquid crystallinity in the polyquinoline, although the introduction of the alkylene spacer alone did not induce it. In addition, polyquinolines substituted with methyl, methoxy, and chloro groups exhibited larger mesophase temperature ranges as well as higher T_ms and T_is than the unsubstituted ones. Tensile strengths of these thermotropic polyquinolines were considerably high in the range of 770 to 1170 kgf/cm². © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 749–759, 1998