Odd Number Of Methylene Groups Research Articles

Effect of Flexible Spacers on the Rheological Behavior of Main-Chain Thermotropic Liquid-Crystalline Polymers Having Bulky Pendent Side Groups

The effect of flexible spacers on the rheological behavior of main-chain thermotropic liquid-crystalline polymers having bulky pendent side groups, poly[(phenylsulfonyl)-p-phenylenealkylenebis(4-oxybenzoate)]s (PSHQn), was investigated. For the study we synthesized a homologous series of PSHQn polymers containing methylene groups, varying from 3 to 12, as the flexible spacer and then investigated their transient, steady-state, and oscillatory shear flow behaviors using a cone-and-plate rheometer. We identified the factors which give rise to, during experiment, time-dependent rheological behavior by taking wide-angle X-ray diffraction (WAXD) patterns of the specimen right before and after each rheological measurement. The initial conditions (i.e., the initial morphology) for transient shear flow were controlled by first heating an as-cast specimen to the isotropic region, shearing there at a rate of 0.1 s-1 for ca. 10 min, and then cooling slowly to a preset temperature in the nematic region. Only positive values of steady-state first normal stress difference were observed in all the PSHQn polymers synthesized, except for PSHQ3 having 3 methylene groups of flexible spacer, at all temperatures and shear rates investigated. Interestingly enough, we found that PSHQ3 exhibits Newtonian behavior at low shear rates over the entire range of temperatures tested, showing no evidence of liquid crystallinity from a rheological point of view. This observation is consistent with our earlier findings based on differential scanning calorimetry and WAXD that PSHQ3 is a glassy, non-liquid-crystalline homopolyester. When steady-state shear viscosity (η) in the nematic region is plotted against T − TNI, where T is a measurement temperature and TNI is a clearing temperature, we found that PSHQn moieties with odd numbers of methylene groups have higher values of η in the nematic region compared to PSHQn moieties with even numbers of methylene groups of the flexible spacer.

Polarization and Internal Electric Field in Aromatic Polyamides Based on m-Xylylenediamine with Linear Aliphatic Dicarboxylic Acids

Polarization reversal and internal electric field were studied for the aromatic polyamides of m-xylylenediamine (MXD) with linear aliphatic dicarboxylic acids in which the number of methylene groups is in the range of 4−10. Polarization reversal was measured for all MXD polyamides at room temperature and at a temperature just above the glass transition temperature (Tg). Large polarization was measured for the polyamides with odd numbers of methylene groups in a dicarboxylic acid unit poled at temperatures above Tg. Internal electric field was measured from the electrochromic spectrum shift and broadening of the probe molecule of 4-(dimethylamino)-4‘-nitrostilbene in the polyamides with even numbers of methylene groups in a dicarboxylic acid unit. Large internal electric field was measured for the samples in which the remanent polarization measured from the polarization reversal is small. The large internal electric field is mainly ascribed to the space charges created by the injected charges. Upon thermal...

Synthesis and characterization of a homologous series of aromatic-aliphatic polyesters with non-coplanar 2,2′-dimethylbiphenylene units

We report on the synthesis and characterization of a series of semiflexible polyesters containing a non-coplanar biphenylene unit and a flexible alkylene spacer of variable length. The number of methylene groups in the spacer was varied from three to eight. The polyesters were synthesized by interfacial polycondensation. The polymer properties were characterized by thermal analysis, optical microscopy and wide-angle X-ray diffraction. Melting transitions and glass transition temperatures show a strong odd-even effect with respect to the number of methylene groups in the flexible spacer. The crystallinity is reduced by the incorporation of the 2,2′-dimethylbiphenylene unit. In the polyesters with an odd number of methylene groups the crystallization is suppressed and indications of a crystalline phase were only observable after extensive annealing.

Sequence Selective Molecular Recognition of Long DNA Sequences by Oligomethylene-Linked Oligoimidazole Analogs of Distamycin

We have studied a series of homologous N-to-N oligomethylene linked bis(diimidazole) analogs 4a-f (number of methylene groups = 1 to 6, re spectively) and a dipicolinamide congener 4g that bind to long GC-containing sequences of DNA. Results from an ethidium binding assay reveal that, for 4a-f, the compounds with an even number of methylene groups have larger ap parent binding constants, Kapp, than those with an odd number. The Kapp values of the compounds with an odd number of methylene groups are close to that of their monomeric analog 3 suggesting that they may be binding to DNA in a monodentate fashion. The binding of these compounds to T4 DNA and their larger binding constants for poly(dG-dC) over poly(dA-dT) indicated minor groove binding selectivity and tolerance for GC sequences. The ability of com pounds 4b-f to bind selectively to DNA was illustrated by an MPE-Fe(II) foot printing study which showed that compound 4f gave the most distinct foot prints. CD titration studies on compounds 4b, d, and f further demonstrated the GC tolerance of these compounds and that they can bind to 7 ~ 8 base pairs of DNA in a bidentate fashion. The minor groove and bidentate bind ing of the ethylene linked compound 4b on the underlined sequence of

Thermal transitions in poly(alkyl-4,4?-diphenoxy terephthalate)s

The thermal transitions of poly(alkyl-4,4′-diphenoxy terephthalate)s, in which the flexible spacer contains 5,6 and 7 methylene groups, have been studied by thermogravimetry, differential scanning calorimetry, X ray diffraction, thermoptical microscopy and small angle light scattering. The series shows a marked influence of the even and odd number of methylene groups on the crystal-liquid crystal transition temperatures and on the isotropization transition temperature. Nematic mesophases have been observed for the odd terms, and a transition from a smectic to a nematic mesophase has been observed for the even term.

Crosslinked liquid crystal polymers from liquid crystal monomers: Synthesis and mechanical properties

AbstractDifunctional acrylates and methacrylate monomers have been made which are high order smectic liquid crystal (or crystalline) at room temperature. This report discusses materials with the following structure: F–S–M–S–F, where F is a functional group, acrylate or methacrylate (A or M); S is a spacer (CH2)n(n), and M is a mesogen—in this case 4,4′‐dioxybiphenyl (B). They are codified as BnA or BnM where n is the number of methylenes in the spacer. High conversion with high Tg can be obtained when polymerizing in the smectic state because the reactive end groups are concentrated in a small volume and can react well with little or no diffusion. B2A, B3A, B6A, B11A, and B3M were polymerized in the smectic state and compared to polymers made at temperatures where the monomers were isotropic. High conversion was obtained below final Tg—even then, probably because the polymers were ordered. All the polymers were studied by WAXD and dynamic mechanical spectroscopy. Solid‐state NMR on B3A showed that there was very high conversion of the double bonds at all temperatures. B3A photopolymerized in the smectic state (60–76°C) produced a crystalline polymer with Tg = 185°C (1 Hz). When photopolymerized at 85°C, above the isotropization temperature (Ti), a poorly organized polymer was obtained with a Tg of 155°C (1 Hz). Monomers with an odd number of methylene groups as spacers were crystalline after polymerization. With an even number of methylene groups, they lost most of their crystallinity on polymerization below Ti, but retained a low order smectic structure. Similar structures were obtained with all the monomers when they were polymerized above Ti. There was little effect of polymerization temperature on Tg when the spacers had an even number of methylene groups. © 1993 John Wiley & Sons, Inc.

Dielectric spectroscopy on liquid‐crystalline main chain polymers with crossing mesogens

AbstractA newly synthesized series of liquid‐crystalline main chain polymers with crossing mesogens is investigated using dielectric spectroscopy. The crossing mesogenic units are endowed with hexyl as well as with CN‐wing groups. We examined the change of mobility of these crossing segments with increasing spacer length in the main chain, the relaxation behaviour at the phase transition nematic‐isotropic and the temperature dependence of the absorption intensity. The main results are: there is an alternation of the dielectric relaxation times with respect to the length of the spacer in such a way that the molecular mobility is raised in case of an odd number of methylene groups in the spacer. The steps in the relaxation frequencies at the clearing temperatures are obviously due to a change in the short‐range order caused by the formation of the nematic structure. Owing to a strong dipol‐dipol interaction between neighbouring segments, a decrease of the absorption intensity with decreasing temperature was observed. Furthermore, apart from the low‐frequency absorption a high‐frequency relaxation process could be monitored.

Polymers with rigid anisotropic side groups: 2. Synthesis and properties of some side chain acrylate and methacrylate liquid crystal polymers containing the 4′-alkylbiphenyl-4-yl moiety

A number of acrylate and methacrylate side chain polymers in which the mesogenic moiety is either a 4′-n-pentyl- or 4′-(2-methylbutyl)-biphenyl-4-yl group have been synthesized. A systematic investigation into the effect on the thermal properties of the acrylate polymers containing the n-pentylbiphenylyl moiety, by changing the size of the flexible spacer group, has revealed large differences in the smectic thermal stability of these polymers with respect to whether the flexible spacer group contains an even or odd number of methylene groups. An explanation is given as to why this alternation effect was observed. X-ray diffraction has shown the smectic phase to be S A in type with a near perfect bilayered structure for the polyacrylates, but a more disordered bilayered structure for the methacrylates. Two of the acrylate polymers exhibit a second smectic phase which has not yet been identified.

Trends in Kinetic Behavior during Ester-Ester Exchange Reactions in Polyesters by Mass Spectrometry. I

Abstract The kinetics of the ester-ester exchange reaction between polyesters from adipic acid and various linear and branched glycols were investigated by mass spectometry using the dimer analysis method (DAM). Rate constants, activation energies, and frequency factors are given for reactions studied in the temperature range of 572–585 K. Correlation of glycol methylene ratios with activation energies and frequency factors shows an alternating trend in kinetic behavior. Reaction systems containing even numbers of methylene groups in the glycol moiety of the reactants exhibited slower reaction rates than systems with odd numbers of methylene groups, while branched reaction systems followed very similar trends when the influence of pendant groups is ignored.

Electrical properties of TCNQ complex salts with polycations containing sulfur atoms in the main chain

AbstractThe electrical properties of complex anion radical salts of 7,7′,8,8′‐tetracyanoquinodimethane with polycations containing sulfur atoms in the main chain were investigated. The influence of the chemical structure of complex and simple salts on their electrical properties is discussed. Complex salts Ks[x, y] containing an odd number of methylene groups between positively charged sulfur atoms show higher electrical conductivity than those with even number of methylene groups between positively charged sulfur atoms. It was found that with simple salts the electrical conductivity increases with the decrease of the distance between S+. For complex salts the electrical conductivity increases if the distance between the donor centers increases. The lowest resistivity values ϱ = 6.46 Ω. cm were found with the complex salts Ks [5,6], whereas the thermal activation energy amounted to 0.015 eV. Electrical properties of these complexes were compared with that of TCNQ complexes with x‐y ionenes.

The Existence of Two Distinct Levels of Order in Thermotropic Nematic Polyesters

Abstract It is shown by means of x-ray diffraction and PMR broad line spectroscopy, that the structure of the flexible spacer drastically influences the order within the nematic phase of thermotropic polyesters based on the 4,4′ - dioxy- 2, 2′-dimethyl azoxybenzene moiety. The existence of two distinct molecular arrangements is proposed: one is characterized by an unusually high degree alignment of macromolecules, the other by a lower degree of alignment. The former is displayed by spacers with an even number of methylene units in the alkanedioic acid moiety of the spacer (odd number of bonds); the latter by a certain number of flexible spacer moieties with an odd number of methylene groups (even number of bonds), as well as in mixed spacers irregularly alternating along the macromolecular chain (copolyesters).

On the crystallinity of poly(alkylbenzimidazole) salts

AbstractPoly(alkyldibenzimidazole) and poly(alkylbisbenzimidazole) having five, six, seven, and eight methylene groups in each repeat unit were synthesized. Salts of these polymers with strong acids, whose pK is 4.00 or less, were prepared. Weaker acids do not form salts with the poly(alkylbenzimidazole)s. It was found that polymers having an even number of methylene groups per repeat unit tend to form crystalline salts while those polymers having an odd number of methylene groups from only amorphous salts. From among the crystalline salts, those containing poly(bisbenzimidazole)s are more crystalline than their analogous poly(dibenzimidazole)s.

Identification of sources of hydrogen atoms in fatty acids synthesized using deuterated water and stereospecifically deuterium labelled NADPH by gas chromatographic mass spectrometric analysis

The mechanism of hydrogen incorporation into fatty acids with rat liver fatty acid synthetase was investigated. The distributions of deuterium atoms incorporated into the fatty acids from D2O and stereospecifically deuterium labelled NADPH were determined by mass chromatography. In palmitic acid, 14 deuterium atoms were incorporated from D2O and were found on the even-numbered methylene carbon atoms (two deuterium atoms per carbon atom). Seven of these 14 deuterium atoms were incorporated as the result of deuterium–hydrogen exchange between the methylene group of malonyl-CoA and C2O and D2O. Seven deuterium atoms came from the 4α-position of NADPH and were found on the odd-numbered methylene carbon atoms (one deuterium atom per carbon atom). Seven deuterium atoms from the 4β-position of NADPH were also found on the odd-numbered methylene carbon atoms (one deuterium atom per carbon atom). The stereospecificities of β-ketoacyl reductase and enoyl reductase for NADPH were determined with S-acetoacetyl-N-acetyl-cysteamine and S-crotonyl-N-acetylcysteamine as substrates. The products, S-hydroxybutryl-N-acetyl-cysteamine and S-butyryl-N-acetylcysteamine, respectively, were analysed by gas chromatography mass spectrometry; the results indicated that the β-ketoacyl reductase had B stereospecificity and enoyl reductase had A stereospecificity for NADPH.

Origin of Hydrogen Atoms in the Fatty Acids Synthesized with Yeast Fatty Acid Synthetase1

The mechanism of hydrogen incorporation into fatty acids was investigated with an enzyme preparation from baker's yeast. Fatty acids synthesized from malonyl-CoA and acetyl-CoA in the presence of D2O or stereospecifically deuterium-labeled NADPH were isolated and analyzed by mass chromatography to examine the localization of deuterium atoms in the molecule. The following results were obtained: 1. Hydrogen atoms from water were found on the even-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom). The second hydrogen atom was incorporated as the result of hydrogen exchange phenomenon between the methylene group of malonyl CoA and water. 2. HB hydrogen of NADPH was used for beta-ketoacyl reductase. 3. HB hydrogen of NADPH was also used for enoyl reductase. 4. Hydrogen atoms from HB position of NADPH were found on the odd-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom).

Stereochemical studies of hydrogen incorporation from nucleotides with fatty acid synthetase from Brevibacterium ammoniagenes.

The biosynthesis of fatty acids from malonyl-CoA and acetyl-CoA was investigated with an enzyme preparation which was purified 100-fold from Brevibacterium ammoniagenes. Fatty acids synthesized in the presence of D2O and stereospecifically deuterated NADPH and NADH were isolated and analyzed by mass chromatography to examine the localization of deuterium in the molecule. The following results were obtained: 1) HB hydrogen of NADPH was used for beta-ketoacyl reductase. 2) HB hydrogen of NADH was used for enoyl reductase. 3) Hydrogen atoms from water were found on the even-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom) and some were also found on the odd-numbered methylene carbon atoms. 4) Hydrogen atoms from NADPH was found on the odd-numbered methylene carbon atoms (1 hydrogen per carbon). 5) Hydrogen atoms from NADH was also found on the odd-numbered methylene carbon atoms, but the number of incorporated hydrogen atoms was less than expected. The exchange of HB hydrogen of NADH with water catalyzed by enoyl reductase was suspected. 6) The exchange of methylene hydrogen atoms of malonyl-CoA with protons of water was suggested by 13C NMR analysis.

Stereochemical studies of hydrogen incorporation from nucleotides with fatty acid synthetase from Brevibacterium ammoniagenes.

The biosynthesis of fatty acids from malonyl-CoA and acetyl-CoA was investigated with an enzyme preparation which was purified 100-fold from Brevibacterium ammoniagenes. Fatty acids synthesized in the presence of D2O and stereospecifically deuterated NADPH and NADH were isolated and analyzed by mass chromatography to examine the localization of deuterium in the molecule. The following results were obtained: 1) HB hydrogen of NADPH was used for beta-ketoacyl reductase. 2) HB hydrogen of NADH was used for enoyl reductase. 3) Hydrogen atoms from water were found on the even-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom) and some were also found on the odd-numbered methylene carbon. 4) Hydrogen atoms from NADPH were found on odd-numbered methylene carbon atoms (1-hydrogen per carbon). 5) Hydrogen atoms from NADH were also found on the odd-numbered methylene carbon atoms, but the number of incorporated hydrogen atoms was less than expected. The exchange of HB hydrogen of NADH with water catalyzed by enoyl reductase was suspected. 6) The exchange of methylene hydrogen atoms of malonyl-CoA with proton of water was suggested by 13C NMR analysis.

Molecular motion in polyamides

AbstractIt is well known that aliphatic polyamides with even numbers of methylene groups between amide groups melt at higher temperatures than those with odd numbers of methylene groups. Crystallographic studies in the past have sought to relate the packing of the amide groups to the variations in melting point, but these studies have been made almost exclusively at room temperature. In the present study, series of polyamide fibers were examined by x‐ray diffraction over a wide range of temperatures. In the even‐numbered polyamides, the triclinic structure occurring at room temperature shifts to a more symmetrical structure in which the chains assume hexagonal packing. This latter packing occurs in the odd‐numbered polymers at room temperature. The polar groups in the latter occur in layers which are normal to the chain axes. The layers of polar groups in the even‐numbered polyamides are tilted with respect to the chain axes at room temperature, and remain tilted at high temperatures even though the lateral chain packing becomes the same as the lower‐melting (odd‐numbered) members of the series. The spacing between polar groups along the chain decreases with increasing temperature, but the decrease is relatively less in the even‐numbered than in the odd‐numbered polymers, and is less in the more polar than in the more paraffinic compounds. These changes are ascribed to torsional and rotational motions of chain segments in the crystallites. Proton magnetic resonance studies demonstrate the onset of motion of the hydrocarbon segments and compare qualitatively the constraints to chain motion among isomeric members of the series. Some implications regarding the melting process are discussed.

STUDIES ON THE SYNTHETIC FIBRE OF THE POLYESTER AMIDE

Linear ester amide copolymers were made from β-hydroxy ethyl ammonium sebacate (I) and salt which were prepared from polymethylene dicarboxylic acid (II) and polymethylene diamine (III) by the equimolar reaction.The polymethylene diamine (III), which have 2_??_12 methylene groups, except for 3 methylene groups, were made dy reduction of aliphatic dinitriles using Raney Ni catalyst.Suitable polymers were not obtained from dicarboxylic acids (II), which has less than 5 carbon chains, due to the accompanied depolymerization. When ethylene diamine was used as diamine, it gave the rubber-like polymer. The melting point of the polymer was over 203°C.Copolymers from (I) and of polymethylene diammonium sebacate (salt of (II) and, (III)), which have more than 4 carbon chains, could be spun very easily from molton state into light coloured or non-coloured and lustrous monofilament of 20_??_150 denier. It was drawn mechanically to 4.5_??_6 times as long as its original length without delay, the tensile strength of all fibers obtained by above method lay in the range of 1.0 to 3.2g/denier and the melting points lay in the range of 149 to 198°C.Diamines which have the odd number of methylene groups give the series of copolymers which have lower melting point and lower value of strength as compared with the groups of diamines which have the even number of methylene. The most excellent copolymers were made from β-hydroxy ethyl ammonium sebacate and tetra methylene diammonium sebacate. The tensile strength of the copolymer was 1.9_??_3.2g/denier and melting point 198°C.

STUDIES ON THE SYNTHETIC FIBRE OF THE POLYESTER AMIDE

Linear ester amide copolymers were made from β-hydroxy ethyl ammonium sebacate (I) and salt which were prepared from polymethylene dicarboxylic acid (II) and polymethylene diamine (III) by the equimolar reaction.The polymethylene diamine (III), which have 2_??_12 methylene groups, except for 3 methylene groups, were made dy reduction of aliphatic dinitriles using Raney Ni catalyst.Suitable polymers were not obtained from dicarboxylic acids (II), which has less than 5 carbon chains, due to the accompanied depolymerization. When ethylene diamine was used as diamine, it gave the rubber-like polymer. The melting point of the polymer was over 203°C.Copolymers from (I) and of polymethylene diammonium sebacate (salt of (II) and, (III)), which have more than 4 carbon chains, could be spun very easily from molton state into light coloured or non-coloured and lustrous monofilament of 20_??_150 denier. It was drawn mechanically to 4.5_??_6 times as long as its original length without delay, the tensile strength of all fibers obtained by above method lay in the range of 1.0 to 3.2g/denier and the melting points lay in the range of 149 to 198°C.Diamines which have the odd number of methylene groups give the series of copolymers which have lower melting point and lower value of strength as compared with the groups of diamines which have the even number of methylene. The most excellent copolymers were made from β-hydroxy ethyl ammonium sebacate and tetra methylene diammonium sebacate. The tensile strength of the copolymer was 1.9_??_3.2g/denier and melting point 198°C.