Synthesis and Properties of Polyurethanes of Hexamethylene Di-Isocyanate with Multifunctional Chromophores in the Main Chain

Various polyurethanes containing photoactive bis(azo) and bis(o-nitrobenzyl) groups in the main chain were synthesized by polyaddition reactions of diols such as bis(4-hydroxyphenylazo)-2,20-dinitrodiphenylmethane, 4-hydroxy-3-methylphenylazo- 40-hydroxyphenylazo-2,20-dinitrodiphenylmethane and bis(4-hydroxy-3- methylphenylazo)-2,20-dinitrodiphenylmethane with hexamethylene di-isocyanate (HMDI), in dimethyl acetamide (DMAc) in the presence of di-n-butyltin dilaurate (DBTDL) as catalyst. All of them were characterized by IR, UV-vis, 1H NMR and 13C NMR spectra and also by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC).

Temperature-responsive properties and drug solubilization capacity of amphiphilic copolymers based on N-vinylpyrrolidone and vinyl propyl ether

A series of amphiphilic copolymers were synthesized by free-radical copolymerization of N-vinylpyrrolidone (NVP) with vinyl propyl ether (VPE), and the structure of the copolymers was characterized by elemental analysis and gel permeation chromatography. The reactivity of VPE in copolymerization was found to be significantly lower than the reactivity of NVP, which resulted in a decrease of copolymers’ yields and molecular weights with higher content of VPE in the feed mixture. An investigation of the behavior of the copolymers in aqueous solutions at different temperatures by dynamic light scattering revealed the presence of lower critical solution temperature, which depending on the content of VPE ranged within 23−38 °C. Aqueous solutions of these copolymers were studied by fluorescent spectroscopy with pyrene as a polarity probe to reveal the formation of hydrophobic domains. The copolymers were found to be useful for enhancing the solubility of riboflavin in water.

Ring-chain interconversion in high-performance polymer systems. 3. Cyclodepolymerization of poly(m-phenylene isophthalamide) (Nomex) and entropically driven ring-opening polymerization of the macrocyclic oligomers so produced

A homologous series of macrocyclic oligoamides has been prepared in high yield by reaction of isophthaloyl chloride with m-phenylenediamine under pseudo-high-dilution conditions. The products were characterized by infrared and H-1 NMR spectroscopies, matrix assisted laser desorption-ionization time-of-flight mass spectrometry, and gel permeation chromatography (GPC). A series of linear oligomers was prepared for comparison. The macrocycles ranged in size from the cyclic trimer up to at least the cyclic nonamer (90 ring atoms). The same homologous series of macrocyclic oligomers was prepared in high yield by the cyclodepolymerization of poly(m-phenylene isophthalamide) (Nomex). Cyclodepolymerization was best achieved by treating a 1% w/v solution of the polymer in dimethyl sulfoxide containing calcium chloride or lithium chloride with 3-4 mol % of sodium hydride or the sodium salt of benzanilide at 150 degreesC for 70 h. Treatment of a concentrated solution of the macrocyclic oligomers (25% w/v) with 4 mol % of sodium hydride or the sodium salt of benzanilide in a solution of lithium chloride in dimethyl sulfoxide at 170 degreesC for 6 h resulted in efficient entropically driven ring-opening polymerizations to give poly(m-phenylene isophthalamide), characterized by infrared and H-1 NMR spectroscopies and by GPC. The molecular weights obtained were comparable with those of the commercial polymer.

Synthesis of hyperbranched poly(aryl ether)s via carbene insertion processes

Homopolymerization of alkylarylcarbenes derived from diazirine monomers that featured benzyl alcohol or phenol residues was found to lead to the production of soluble hyperbranched poly(aryl ether)s. The polymerization process was influenced by the solvents employed, monomer concentration, and the reaction time. An increase in the monomer concentration and reaction time was found to lead to an increase in the molecular weight characteristics of the resulting polymers as determined by gel permeation chromatography (GPC). The composition and architecture of the polyethers were determined by nuclear magnetic resonance (NMR) spectroscopic analysis and were found to be highly complex and dependent on the structure of the monomers used. All of the polymers were found to contain ether linkages formed via carbene insertion into O-H bonds, although polymers derived from phenolic carbenes also contained linkages arising from C-alkylation.

Synthesis of hyperbranched poly(aryl amine)s via a carbene insertion approach

A novel diazirine functionalised aniline derivative, 3-(3-aminophenyl)-3-methyldiazirine 1, was prepared and employed as an AB(2)-type monomer in the synthesis of hyperbranched polymers; thus providing the first instance in which polyamines have been prepared via carbene insertion polymerisation. Photolysis of the monomer 1 in bulk and in solution resulted in the formation of hyperbranched poly(aryl amine)s with degrees of polymerisation (DP) varying from 9 to 26 as determined by gel permeation chromatography (GPC). In solution, an increase in the initial monomer concentration was generally found to result in a decrease in the molecular weight characteristics of the resulting poly(aryl amine) s. Subsequent thermal treatment of the poly(aryl amine) s caused a further increase in the DP values up to a maximum of 31. Nuclear magnetic resonance (NMR) spectroscopic analysis revealed that the increase in molecular weight upon thermal treatment resulted from hydroamination of styrenic species formed in the initial photopolymerisation or activation of diazirine moieties.

Reversible, nondegradative conversion of crystalline aromatic poly(ether ketone)s into organo-soluble poly(ether dithioketal)s

Crystalline aromatic poly(ether ketone)s Such as PEEK and PEK may be cleanly and reversibly derivatized by dithioketalization of the carbonyl groups With 1,2-ethanedithiol or 1,3-propanedithiol under strong acid conditions. The resulting 1,3-dithiolane and 1,3-dithiane polymers are hydrolytically stable, amorphous, and readily soluble in organic solvents such as chloroform and THF and are thus (unlike their parent polymers) easily characterized by gel permeation chromatography (GPC). GPC analysis of a range of derivatized PEEK samples using light-scattering detection revealed, in some instances, a bimodal molecular weight distribution with a small but potentially significant (and previously undetected) very high-molecular-weight fraction.

Block copolymers of ethylene oxide and phenyl glycidyl ether: micellization, gelation, and drug solubilization

Three triblock copolymers of ethylene oxide and phenyl glycidyl ether, type E(m)G(n)E(m), where G = OCH2-CH(CH2OC6H5) and E = OCH2CH2, were synthesized and characterized by gel-permeation chromatography, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, and NMR spectroscopy. Their association properties in aqueous solution were investigated by surface tensiometry and light scattering, yielding values of the critical micelle concentration (cmc), the hydrodynamic radius, and the association number. Gel boundaries in concentrated micellar solution were investigated by tube inversion, and for one copolymer, the temperature and frequency dependence of the dynamic moduli served to confirm and extend the phase diagram and to highlight gel properties. Small-angle X-ray scattering was used to investigate gel structure. The overall aim of the work was to define a block copolymer micellar system with better solubilization capacity for poorly soluble aromatic drugs than had been achieved so far by use of block copoly(oxyalkylene)s. Judged by the solubilization of griseofulvin in aqueous solutions of the E(m)G(n)E(m) copolymers, this aim was achieved.

Cinnamate ester containing liquid crystalline side chain polymers

The synthesis of methacrylate esters of 4-cyanophenyl-(4-(ω-hydroxyalkyloxy)) cinnamates, with spacer lengths of 2 and 6 methylene units and the synthesis of the corresponding acrylate ester with a spacer of 2 methylene units are described. The methacrylate monomers were polymerized by free radical polymerization, both as homopolymers and as copolymers with the analogous benzoate monomer of spacer length 6. The acrylate ester could not be polymerized successfully under the same reaction conditions. Polymers were characterized by NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermo-optic observations. Of the monomers prepared, only the cinnamate with a hexamethylene spacer shows a mesophase, seen on supercooling of the melt. All of the polymers prepared were liquid crystalline, with smectic behavior predominating in the polymethacrylates with the longer spacer group. A narrow nematic region is seen just below the clearing temperature with a range of 3–9°C, nematic character is increased in the copolymer series with the degree of incorporation of the cinnamate monomer with the spacer group of length 2.

Exploring variation in proanthocyanidin composition and content of sainfoin (Onobrychis viciifolia)

To maximise the potential benefits to ruminants from sainfoin, plant breeding should focus on developing varieties with predictable condensed tannin (CT) profiles. Little is known about whether and to what extent accession and environment influence sainfoin CT structures. We sought to investigate the likely extent of accession and environment effects on CT characteristics of sainfoin. Four single-flowering (Communis) accessions and two multiple-flowering (Bifera) accessions, grown at three sites and collected at two harvest times were used. Sainfoin CTs were characterised by thiolytic degradation and by high-performance liquid chromatography-gel permeation chromatography (HPLC-GPC). Also, CT concentration measured earlier by the HCl-butanol method was compared with that from thiolysis

Exploring variation in procyanidin composition and content of sainfoin (Onobrychis viciifolia)

Abstract BACKGROUND: To maximise the potential benefits to ruminants from sainfoin, plant breeding should focus on developing varieties with predictable condensed tannin (CT) profiles. Little is known about whether and to what extent accession and environment influence sainfoin CT structures. We sought to investigate the likely extent of accession and environment effects on CT characteristics of sainfoin. Four single-flowering (Communis) accessions and two multiple-flowering (Bifera) accessions, grown at three sites and collected at two harvest times were used. Sainfoin CTs were characterised by thiolytic degradation and by high-performance liquid chromatography-gel permeation chromatography (HPLC-GPC). Also, CT concentration measured earlier by the HCl-butanol method was compared with that from thiolysis. RESULTS: Thiolysis revealed that accession and harvest influenced most CT structural attributes. Bifera CTs eluted as single peaks (Mp  < 6220 Da) in HPLC-GPC across the two harvests and two sites, whereas Communis generated two to three CT peaks, which included a peak (Mp  ≤ 9066 Da) in the second harvest. A discrepancy was observed in CT concentrations measured by the two methods. CONCLUSION: CTs from Bifera accessions had more stable and predictable characteristics across harvests and sites and this could be of interest when breeding sainfoin. © 2013 Society of Chemical Industry.

Biosynthesis and characterization of biodegradable Poly(3-hydroxybutyrate) from renewable sources

Poly(3-hydroxybutyrate) was produced in fed-batch cultures of Ralstonia eutropha DSM 428 and Alcaligenes latus ATCC 29712 on a mineral medium with different carbon sources such as sucrose, sodium lactate, lactic acid, soybean oil and fatty acid. The bacteria converted the different carbon sources supplied into P3HB. The best results were obtained when lactate or soybean oil were supplied as the sole carbon source. The range of number average molar mass (Mn) for the polymers, analyzed by Gel Permeation Chromatography was 1.65 to 0.79 x 10(5) g mol(-1). FTIR spectroscopy revealed a characteristic absorbance associated with polyester structures. The crystallinity degree, determinate from X-ray diffractograms, was about 69% in all synthesized polymers. The thermal properties associated to semicrystalline polymers indicated a glass transition at 0.1 degrees C and a melting point at about 175 degrees C and enthalpy of 63-89 J g(-1). The (1)H-NMR and (13)C-NMR spectra of the polymers were in agreement with the calculated chemical shifts associated with P3HB structures.

Crystalline particles from self-assembled divinyl oligomers

Ethylene glycol dimethacrylate (EGDMA) and/or triethylene glycol dimethacrylate (TEGDMA) oligomers formation was catalyzed in aqueous medium by horseradish peroxidase (HRP) in the presence of H(2)O(2) at room temperature. EGDMA and/or TEGDMA oligomers were characterized by means of gel permeation chromatography, infrared vibrational spectroscopy and (1)H NMR spectroscopy. Self-assembling of oligomers led to right-angled crystalline particles, as evidenced by scanning electron microscopy and differential scanning calorimetry. EGDMA, TEGDMA and EGDMA-co-TEGDMA oligomers synthesized in the presence of HRP-H(2)O(2) system presented pendant vinyl groups along the chains. good solubility in chloroform, and well-defined melting point. These features evidenced few cross-linking or cyclization and revealed that the catalytic properties of HRP led to oligomeric materials with new characteristics. (C) 2008 Elsevier B.V. All rights reserved.

Monodisperse lignin fractions as standards in size-exclusion analysis Comparison with polystyrene standards

The difficulty of preparing monodisperse lignin fractions on a large scale is a limiting factor in many applications. The present paper addresses this problem by examining the properties and size-exclusion behavior of lignin isolated by the acetosolv pulping process from post-extraction crushed sugarcane bagasse. The isolated lignin was subjected to a solvent pretreatment, followed by preparative gel permeation chromatography fractionation. The fractions were analyzed by high-performance size-exclusion chromatography (HPSEC) and these samples showed a great decrease in polydispersity, compared to the original acetosolv lignin. Several fractions of very low polydispersity, close to unity, were employed as calibration curve standards in HPSEC analysis. This original analytical approach allowed calibration with these lignin fractions to be compared with the polystyrene standards that are universally employed for lignin molecular mass determination. This led to a noteworthy result, namely that the lignin fractions and polystyrene standards showed very similar behavior over a large range of molecular masses in a typical HPSEC analysis of acetosolv lignin. (C) 2009 Elsevier B.V. All rights reserved.

Molecular mass distribution of dextran in Brazilian sugar and insoluble deposits of cachaca

The dextran molecular mass distribution profile in 77 sugar samples from Brazil and twelve insoluble deposits (alcoholic flocks) samples from sugared cachacas (Brazilian sugar cane spirit) is described in terms of number-average molecular mass M,,, weight-average molecular mass M(w), Z-average molecular mass M,, and polydispersity. The analyses were performed by size-exclusion chromatography, using a refractive index detector. In most of the sugar samples, it was possible to identify two major groups of dextrans with Mw averages of 5 x 10(6) and 5 x 10(4) Da. Based on the evaluated parameters, the dextran distribution profile is about the same in samples analyzed over five seasons, and, therefore, it is likely that the Brazilian product pattern will not change very much over the years. In insoluble deposits from sugared cachacas, dextrans with Mw values in the order of the 10(5) Da were the most frequent ones, being present in 58% of the samples. (c) 2008 Elsevier Ltd. All rights reserved.

Structural characterization of Botryosphaeran: a (1 -> 3;1 -> 6)-beta-D-glucan produced by the ascomyceteous fungus, Botryosphaeria sp.

The exopolysaccharide, Botryosphaeran, produced by the ligninolytic, ascomycetcous fungus Botryosphaeria sp., was isolated from the extracellular fluid by precipitation with ethanol, and purified by gel permeation chromatography to yield a carbohydrate-rich fraction (96%) composed mainly of glucose (98%). Infra-red and C-13 NMR spectroscopy showed that all the glucosidic linkages were in the beta-configuration. Data from methylation analysis and Smith degradation indicated that Botryosphaeran was a (1 --> 3)-beta-(D)-glucan with approx 22% side branching at C-6. The products obtained from partial acid hydrolysis demonstrated that the side branches consisted of single (1 --> 6)-beta-linked glucosyl, and (1 --> 6)-beta-linked gentiobiosyl residues.[GRAPHICS](C) 2003 Elsevier Ltd. All rights reserved.