Synthesis and characterization of side-chain liquid-crystalline poly(ether ester)s having p-substituted biphenyl mesogenic side groups

Several novel mesogenic spiro-orthoester monomers such as 1,6,10-trioxaspiro[4,5]decanes 4 , containing biphenyl mesogens at the C-8 positions of the five- and six-membered spirocyclic ring, through the alkylene spacers of different lengths were prepared by condensation reaction of the corresponding biphenyl mesogenic 1,3-propanediol 3 with 2,2-diethoxytetrahydrofuran, with 50–75% yields. Through cationic double ring-opening polymerization, carried out with boron trifluoride etherate as an initiator (5 mol % vs. monomer) in bulk at 150°C, spiro-orthoester monomers 4 afforded a novel class of side-chain thermotropic LC polymers with a poly(ether ester) as the main chain 8 . The liquid-crystalline properties of the spiro-orthoester monomers and the resulting polymers were examined by differential scanning calorimetry and optical polarized microscopy. Biphase separation was observed in the side-chain liquid-crystalline poly(ether ester)s upon annealing in the broad isotropic region. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2439–2455, 1998     

Synthesis and characterization of poly(ethyleneimine) dendrimers

Poly(ethyleneimine) (PEI) dendrimers up to the third generation (G3) were prepared by a divergent synthesis method from an ethylenediamine (EDA) core. The amine terminals were bonded with vinylbromide by a Michael addition reaction. Then, the bromide terminals were converted to amine groups using a Gabriel amine synthesis method. PEI dendrimers displayed pH-dependent luminescence, and their emission intensities at pH 6 increased over time. Fluorescence intensities also increased with increasing dendrimer generation from G1 to G3. Air-bubbling in aqueous solutions of dendrimers made to incorporate detectable amount of oxygen in dendrimers. EDA also behaved similarly in luminescence and oxygen incorporation.

Poly(vinyl ether)s and poly(propenyl ether)s containing mesogenic groups: A new class of side-chain liquid-crystalline polymers

A new series of thermotropic liquid-crystalline polymers, poly(vinyl ether)s and poly(propenyl ether)s, containing the mesogen 4-methoxy-4′-hydroxybiphenyl in the side chain and different spacers between the mesogens and the backbone were synthesized and characterized by DSC and optical microscopy. Their mesomorphic behavior was compared to that of the corresponding polymethacrylates. In general the poly(propenyl ether)s showed lower transition temperatures and larger thermal stability ranges of their mesophases than the respective polymethacrylates, reflecting the effect of substituting the rigid ester bond connecting the spacer to the backbone in polymethacrylates by a more flexible ether bond. Also, poly(propenyl ether)s showed more ordered mesophases than the polymethacrylates, suggesting that a better decoupling of the mesogen and polymer backbone is obtained through the ether linkage.     

Synthesis and characterization of side-chain liquid-crystalline polysiloxanes containing fluorinated units

Several new chiral side-chain LC polysiloxanes (IP–VIIP) bearing fluorinated methyl groups were synthesized with a cholesteric LC monomer and a non-LC monomer containing fluorinated units. The chemical structures and LC properties of the monomers and polymers were characterized by use of various experimental techniques. The effect of copolymer composition on mesomorphic properties of the fluorine-containing polymers was studied as well. The obtained polymers were soluble in many solvents and the specific rotations showed negative values. The temperatures at which 5% weight loss occurred (T _d) were greater than 300 °C for all the polymers and the residue weight on heating to 600 °C increased slightly with increase of the monomer containing fluorinated units in the polymer systems. All the polymers displayed two-phase transitions when they were heated and cooled. The IP, IIP, and IIIP exhibited cholesteric textures when they were heated and cooled, while IVP, VP, VIP, and VIIP showed smectic fan-shaped textures. XRD curves of samples of IVP, VP, VIP, and VIIP displayed sharp and strong peaks at low angle, but no sharp peaks were shown at low angle for the samples IP, IIP, and IIIP.     

Synthesis and characterization of a multiblock copolymer of poly(N-isovaleryl ethyleneimine) and poly(ethylene glycol)

Block copolymers of poly(N-isovaleryl ethyleneimine) (PiVEI) and poly(ethylene glycol) (PEG) were synthesized by coupling previously prepared blocks of PEG ditosylate with the dianion of the dihydroxy PiVEI. On the average four blocks coupled together to form the final block polymer. The PiVEI blocks crystallized with the same melting points as in the homopolymer. This restricted the mobility of the PEG blocks and they did not crystallize unless cooled well below room temperature. The mechanical properties of cast films were quite good with a tensile strength of 77 kg/cm² and an elongation of 120%. The swelling of unoriented and oriented films with water was studied. The unoriented polymer absorbed about its own volume of water, even though PEG comprised only 40% of the total polymer.     

Synthesis and characterization of hyperbranched aromatic poly(ether imide)s with terminal amino groups

We synthesized an AB₂‐type monomer, 4‐{4‐[di(4‐aminophenyl)methyl]phenoxy}phthalic acid, which contained one phthalic acid group and two aminophenyl functionalities. The direct self‐polycondensation of the AB₂‐type monomer in the presence of triphenylphosphite as an activator afforded a hyperbranched poly(ether imide) with a large number of terminal amino groups. This polymer was characterized with ¹H NMR and IR spectroscopy. The degree of branching of the hyperbranched poly(ether imide) was approximately 56%, as determined by a combination of model compound studies and an analysis of ¹H NMR spectroscopy integration data. The terminal amino groups underwent functionalization readily. The solubility and thermal properties of the resulting polymers depended on the nature of the chain end groups. In addition, the hyperbranched poly(ether imide) was grafted with polyhedral oligomeric silsesquioxane (POSS). Transmission electron microscopy analysis revealed that the grafted POSS molecules aggregated to form a nanocomposite material. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3726–3735, 2003     

Dielectric properties of liquid-crystalline copolymers with side cyanobiphenyl groups and acrylic acid units

Dielectric properties of a number of liquid-cry stalline comb-shaped copolymers with different ratios of side-chain mesogenic cyanobiphenyl groups and acrylic acid units are studied. In the electric-field frequency range 300 Hz-100 MHz, temperature dependences of dielectric permittivity are obtained for nematic and isotropic phases. The times of relaxation and the energies of activation for processes responsible for dielectric-permittivity dispersion are measured. The quantitative relationship between the dielectric characteristics and the content of acrylic acid units in the copolymer is established.     

Synthesis and characterization of new cardo poly(bisbenzothiazole-urea)s containing bulky pendant groups

A series of novel rigid poly(bisbenzothiazole-urea)s (PBTUs III) containing bulky pendant groups were synthesized from 2,2-diaminodibenzothiazoles and aromatic diisocyanates conveniently in the mild condition. The inherent viscosity, solubility, thermal stability, morphology, mechanical and photophysical properties of them were investigated and compared in detail. The inherent viscosities were in the range of 0.58-0.73 dL/g. All of the polymers exhibited excellent solubility in various polar organic solvents. They also showed good thermal stability and mechanical properties. The decomposition temperatures at 10% weight loss were in the range of 368-431 °C in nitrogen. All the PBTUs III were amorphous. Tensile strength of PBTUs III showed the range from 85 to 98 MPa. Compared with poly(benzothiazole)s, all the PBTUs III had the larger optical bandgap and lower photoluminescence quantum yields.     

Synthesis and characterization of poly(urethane-sulfone)s

Eight poly(urethane-sulfone)s were synthesized from two sulfone-containing diols, 1,3-bis(3-hydroxypropylsulfonyl)propane (Diol-333) and 1,4-bis(3-hydroxypropylsulfonyl)butane (Diol-343), and three diisocyanates, 1,6-hexamethylene diisocyanate (HMDI), 4,4′-diphenylmethane diisocyanate (MDI), and tolylene diisocyanate (TDI, 2,4- 80%; 2,6-20%). As a comparison, eight polyurethanes were also synthesized from two alkanediols, 1,9-nonanediol and 1,10-decanediol, and three diisocyanates. Diol-333 and Diol-343 were prepared by the addition of 1,3-propanedithiol or 1,4-butanedithiol to allyl alcohol and subsequent oxidation of the resulting sulfide-containing diols. The homopoly(urethanesulfone)s from HMDI and MDI are semicrystalline, and are soluble in m-cresol and hot DMF, DMAC, and DMSO. The copoly(urethane-sulfone)s from a 1/1 molar ratio mixture of Diol-333 and Diol-343 with HMDI or MDI have lower crystallinity and better solubility than the corresponding homopoly(urethane-sulfone)s. The poly(urethane-sulfone)s from TDI are amorphous, and are readily soluble in m-cresol, DMF, DMAC, and DMSO at room temperature. Differential scanning calorimetry data showed that poly(urethane-sulfone)s have higher glass transition temperatures and melting points than the corresponding polyurethanes without sulfone groups. The rise in glass transition temperature is 20–25°C while the rise in melting temperature is 46–71°C. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(amide-sulfonamide)s

Novel poly(amide-sulfonamide)s have been prepared by reacting terephthaloyl, isophthaloyl, and sebacoyl chloride with variously substituted dianilines containing preformed sulfonamide linkages. Inherent viscosities of the prepared polymers ranged from 0.19 to 0.58 dL/g. Despite low apparent viscosities, the polymers had film forming properties. Clear, tough, flexible films were obtained from the prepared polymers, in particular the poly(terephthalamide-sulfonamide)s. Glass transition temperatures, determined by differential scanning calorimetry, ranged from 84 to 247°C. Thermogravimetric analyses of the polymers showed that they have moderate thermal stability with weight losses ranging from 12 to 35% at 350°C.     

Synthesis and characterization of poly(ester-sulfone)s

Aliphatic and aromatic-aliphatic poly(ester-sulfone)s were synthesized by the transesterifications of diphenyl adipate and diphenyl phthalates (ortho, meta, para) with two sulfonecontaining diols, 1,3-bis (3-hydroxypropylsulfonyl) propane (Diol-333) and 1,4-bis(3-hydroxypropylsulfonyl) butane (Diol-343). Based on DSC and WAXD studies, the aliphatic homopoly(ester-sulfone)s are semicrystalline at room temperature and liquid crystalline at elevated temperature, while their copolymers with alkanediols are liquid crystalline. The liquid crystalline phase formation in aliphatic poly(ester-sulfone)s is attributed to the strong dipole-dipole interactions between sulfone groups. The aromatic-aliphatic poly(estersulfone)s from diphenyl phthalate (ortho) and isophthalate (meta) are amorphous. They are soluble in trifluoroacetic acid and m-cresol at room temperature, and DMF, DMAC, and DMSO at elevated temperature. The aromatic-aliphatic poly(ester-sulfone)s from diphenyl terephthalate are semicrystalline and are soluble only in trifluoroacetic acid. For a given diol, the glass transition temperatures of aromatic-aliphatic poly(ester-sulfone)s increase from phthalate to isophthalate to terephthalate. This is because the flexibility of the benzene ring in the polymer backbone decreases from ortho to meta to para substitution. As a comparison, polyesters without sulfone groups were synthesized from two alkanediols, 1,9-nonanediol and 1,10-decanediol, and the diphenyl esters. The poly(ester-sulfone)s have glass transition temperatures 60–80°C higher than the corresponding polyesters without sulfone groups, due to the strong dipolar interactions between sulfone groups. © 1994 John Wiley & Sons, Inc.     

Synthesis of bifunctional monodisperse poly(N-isovaleryl ethyleneimine)

A bifunctional initiator, ethanediyl 1,2-bis(2-isobutyl oxazolinium trifluoromethane sulfonate) was prepared and used for the ring opening polymerization of 2-isobutyl oxazoline. Polymerizations were run in CH₃CN at 80 and 60°C and in sulfolane at 80°C. The molecular weight distributions of the poly(N-isovaleryl ethyleneimine)s produced, M/I ≤ 45, approached Poisson distribution.     

Synthesis,characterization, and properties of linear poly(ether sulfone)s with dendritic terminal groups

Hybrid linear‐dendritic ABA polymers, where A and B are dendritic and linear polymers, respectively, were synthesized in a single step via step‐growth polymerization of 4,4′‐difluorodiphenylsulfone and bisphenol A using arylether ketone dendrons of first and second generations (G1‐OH and G2‐OH) as monofunctional end‐cappers. These G1 and G2‐terminated poly(ether sulfone)s (G1‐PESs and G2‐PESs) were characterized by ¹H NMR, SEC, DSC, TGA, melt rheology, and tensile tests. The comparison of the glass transition temperatures (T_gs) of these polymers with those of t‐butylphenoxy‐terminated polysulfones reveal that the G1‐ and G2‐PESs have lower T_gs at all molecular weights investigated. However, a plot of T_g versus 1/M_n shows that the difference between the three series becomes negligible at infinite molecular weight and agrees to the chain end free volume theory. The melt viscosities of G1‐PES and G2‐PES with high molecular weights do not show a Newtonian region and, in the high frequency region, their viscosities are lower than that of the control while the stress–strain properties are comparable to those of the control, suggesting that it is possible to reduce the high shear melt viscosity of a PES without affecting the stress–strain properties by introducing bulky dendritic terminal groups. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 958–969, 2008     

Synthesis of side-chain regioregular and main-chain alternating poly(bichalcogenophene)s and an ABC-type periodic poly(terchalcogenophene)

Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared. Grignard metathesis of SSeI2, STeI2, SeTeI2, and SSeTeI2 occurred regioselectively at the lighter chalcogenophene site because of its relatively lower electron density and less steric bulk. Nickel-catalyzed Kumada catalyst-transfer polycondensation of these Mg species provided a new class of side-chain regioregular and main-chain AB-type alternating poly(bichalcogenophene)s—PSSe, PSTe, and PSeTe—through a chain-growth mechanism. The ring-walking of the Ni catalyst from the lighter to the heavier chalcogenophene facilitated subsequent oxidative addition, thereby suppressing the possibility of chain-transfer or chain-termination. More significantly, the Ni catalyst could walk over the distance of three rings (ca. 1 nm)—from a thiophene unit via a selenophene unit to a tellurophene unit—to form PSSeTe, the first ABC-type regioregular and periodic poly(terchalcogenophene) comprising three different types of 3-hexylchalcogenophenes.

Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared to synthesize a new class of polychalcogenophenes with precisely controlled sequences by catalyst-transfer polycondensation.     

Synthesis and characterization of aromatic poly(ether sulfone)s containing pendant sodium sulfonate groups

Poly(ether sulfone)s containing pendant sodium sulfonate groups were prepared by the aromatic nucleophilic substitution reaction of 4,4′-dichlorodiphenylsulfone ( 1 ) and sodium 5,5′-sulfonylbis (2-chlorobenzenesulfonate) ( 2 ) with bisphenols ( 3 ) in the presence of potassium carbonate in N,N-dimethylacetamide. A new monomer 2 containing the sodium sulfonate groups was synthesized by the sulfonation of 1 with fuming sulfuric acid. The polycondensation proceeded smoothly at 170°C and produced the desired poly(ether sulfone)s containing the sodium sulfonate with inherent viscosities up to 1.2 dL/g. The polymers were quite soluble in strong acid, dipolar aprotic solvents, m-cresol, and dichloromethane. The thermogravimetry of the polymers showed excellent thermal stability, indicating that 10% weight losses of the polymers were observed in the range above 460°C in nitrogen atmosphere. Both the glass transition temperatures and hydrophilicity of the polymers increased with increasing their concentrations of sodium sulfonate groups. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of thianthrene-containing poly(benzoxazole)s

New thioether- and thianthrene-containing poly(benzoxazole)s (PBOs) were synthesized from 4,4′-thiobis[3-chlorobenzoic acid] and thianthrene-2,7- and -2,8-dicarbonyl chlorides with commercially available bis-o-aminophenols. Polymers were prepared via solution polycondensation in poly(phosphoric acid) at 90–200°C. Transparent PBO films were cast directly from polymerization mixtures or m-cresol. The films were flexible and tough. Non-fluorinated PBOs were soluble only in strong acids and AlCl₃/NO₂R systems by forming complexes with the benzoxazole heterocycle Glass transition temperatures ranged from 298–450°C, and thermogravimetric analysis showed good thermal stabilities in both air and nitrogen atmospheres. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(ether naphthalimide)s

A series of new poly(ether imide)s containing the naphthalimide moiety were prepared from bis(4-fluorobenzoyl)naphthalimides and several bisphenols by aromatic nucleophilic displacement polymerization. These polyimides had inherent viscosities in the range of 0.31–1.04 dL/g in chloroform and glass transition temperatures of 283.0–341.6°C by differential scanning calorimetry. The onset temperature for 5% weight loss for all the polymers was over 448°C, as assessed by thermogravimetry at a heating rate 10°C/min in nitrogen. In addition, these novel polyimides exhibited good solubility in organic solvents including N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, 1,1,2,2-tetrachloroethane and chloroform. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3227–3231, 1999