Preparation of polyamides via the phosphorylation reaction. Poly-4,4′-benzanilides

4,4′-Diaminobenzanilide (DAB) was reacted with diacids via the Yamazaki phosphorylation reaction to yield simple polyamides and random copolyamides. The use of DAB was found to promote polycondensation because DAB contains a preformed amide linkage which minimizes the amounts of by-products formed. It also maximizes polymer solubility since the monomer is unsymmetrical. The order of the inherent viscosity values of the polymers obtained from DAB by reaction with different diacids, isophthalic > aliphatic > terephthalic, was found to parallel polymer solubility in the reaction medium. The inherent viscosity of the polyamide based on terephthalic acid, DAB-T, was increased greatly by copolymerization, isophthalic acid being more effective than an aliphatic diacid in this regard. None of the polymers formed a thermotropic nematic phase, but the copolymer having an equimolar ratio of terephthalic and adipic acid formed anisotropic solutions in 100% sulfuric acid at polymer concentrations exceeding 40%. Strong films were cast from such solutions.     

UV–Vis spectra and structure of acid-base forms of dimethylamino- and aminoazobenzene

The changes in the UV–Vis absorption spectra of dimethylaminoazobenzene (DAB) in the cellulose triacetate (CTA) matrix during the absorption of gaseous hydrogen chloride and protonation of DAB in weakly and strongly acid solutions of hydrochloric and sulfuric acids were studied. The yellow-orange color of DAB and its analog aminoazobenzene (AAB) was shown to be due to the dimers, whose structure involves phenylaminyl type cations formed due to the promotion of the sp ² electrons of the azo groups to the Rydberg R _3s orbitals of the azo groups and possessing Vis bands at 400–417 nm. The cations exist immanently as the dimers due to the Rydberg intermonomer bonds; the Vis bands of the dimers shifted toward 500–520 nm under the action of HCl (in CTA) and weakly acid media as a result of the formation of phenyl aminyl type pair cations, whose π* levels are split by Simpson’s mechanism, during the protonation of interrelated monomers. In the concentrated sulfuric acid, the Vis bands at 500–520 nm vanished because of the decomposition of the dimers into diprotonated monomers possessing Vis bands at 400–417 nm. The mechanism of transformations of chromogens responsible for the spectral transformation was given.     

Transformations of methyl orange dimers in aqueous–acid solutions,according to UV–Vis spectroscopy data

The effect acidity has on the UV–Vis absorption spectra of azo dye methyl orange (MOD) in aqueous solutions of hydrochloric acid in the pH range of 1.7 to 7 and sulfuric acid in the 0.24 to 18 mol/L range of concentrations is investigated. The spectral transformations of MOD solutions are compared to the corresponding spectral transformations of solutions of dimethylaminoazobenzene (DAB), which is an azo dye akin to MOD. A close resemblance between the spectral transformations of MOD and dimers DAB₂ is revealed. It is concluded that the ground state of MOD, like the ground state of DAB, consists of not individual molecules but of supramolecular dimers MOD₂. It is found that dimers MOD₂ in aqueous low-acidic solutions are reversibly protonated with the formation of di- and triprotonated forms, which reversibly dissociate into diprotonated monomers upon an increase in acidity. The structural formulas of the chromogenic groups responsible for the spectral transformations, and the mechanisms of their reversible transformations, are given.     

Stereospecific radical polymerization of N-triphenylmethylmethacrylamides leading to highly isotactic helical polymers

N-Triphenylmethylmethacrylamide (TrMAM) and N-[di(4-butylphenyl)phenylmethyl]methacrylamide (DBuTrMAM) were polymerized using radical initiators. The polymer PTrMAM obtained from TrMAM was insoluble in the common solvents, but was dissolved in sulfuric acid to quantitatively give polymethacrylamide. The 1H NMR spectrum of PTrMAM in sulfuric acid-d2 indicated that the derived polymethacrylamide was nearly 100% isotactic. On the other hand, DBuTrMAM yielded the polymer PDBuTrMAM, which was soluble in THF and chloroform and whose NMR pattern in sulfuric acid-d2 was similar to that of PTrMAM. The polymerization of TrMAM and DBuTrMAM in an optically active solvent, (-)- or (+)-menthol, afforded the optically active polymers having a prevailing one-handed helical structure. The monomers were not solvolized in a methanol-chloroform mixture. TrMAM was not polymerized by anionic initiators.     

Manufacture of xylose-based fermentation media from corncobs by posthydrolysis of autohydrolysis liquors

Milled corncob samples were mixed with water and heated to obtain a liquid phase containing oligosaccharides, sugars, and acetic acid as main reaction products (autohydrolysis reaction). To hydrolyze the sugar oligomers to the correspondent monomers, sulfuric acid was added to the autohydrolysis liquors to reach 0.5–2 wt% of solution, and the reaction media were heated at 101.5–135°C. With this operational procedure, sugar solutions suitable as fermentation media (containing xylose as the major component) were obtained. The kinetics of the posthydrolysis step was characterized on the basis of experimental data concerning the time courses of the concentrations of xylooligosaccharides, xylose, furfural, and acetic acid. The concentrations of other reaction byproducts (glucose or arabinose) were also measured.     

Raman spectra of glycolic acid,l-lactic acid and d,l-lactic acid oligomers

Polymerization of glycolic acid, l- and d,l-lactic acid was followed by Raman spectroscopy in aqueous solution at different concentrations, in viscous and solid states. The Raman spectra of some oligomers obtained by progressive polycondensation of α-hydroxycarboxylic acid aqueous solutions were investigated in the 200–18 cm⁻¹ region. Vibrational analysis revealed the characteristic peaks of ester groups that appeared in the repeat unit of the polymeric chain during the polymerization reaction, and those of the monomers which disappeared. In particular, the ν(CC) stretching vibrations occur in the 800–1000 cm⁻¹ range, which is easily accessible because of the weak diffusion of water. Moreover, spectral monitoring of the semicrystalline sample of poly(glycolic acid) oligomers showed Raman peaks associated with the vibrations of the polymer in the amorphous and semicrystalline states.     

Polymers containing anthraquinone units: Polymers from 1,5-diaminoanthraquinone and aralkyldiketones

Schiff's-base polymers have been formed by the condensation of 1,5-diaminoanthraquinone with 1,4- and 1,3-diacetylbenzene and 2,6-diacetylpyridine. These polymers were soluble in methanesulfonic and concentrated sulfuric acids (1,4-diacetylbenzene polymer) or N,N-dimethylacetamide. The polymer formed from 1,4-diacetylbenzene was ring-closed in polyphosphoric acid to yield a thermally stable polymer soluble in concentrated sulfuric acid which lost only 10% of its weight at 900°C in a TGA test.     

Rigid rod polymers from liquid crystalline phthalocyanines

A number of alkoxy-substituted silicon-dihydroxy-phthalocyanines have been synthesized which form discotic mesophases depending on the side chain length. Metal salt catalyzed polycondensation only gives oligomers while polymer synthesis from activated monomers leads to reasonable high molecular weigths. Indications for the existence of mesophases in this polymer are given.     

Dielectric, physicomechanical, and thermal properties of polymer films prepared from cured 4,4��-divinyldiphenylalkanes

The dielectric, physicomechanical, and thermal properties of crosslinked polymer films prepared by copolymerization of divinyl aromatic monomers and oligomers containing methylene bridges between benzene rings were studied.     

Radiation-induced reactions in poly(1,2,2,2-tetrachloroethyl methacrylate)/monomer mixtures

The work has been aimed at characterizing final products of radiation-induced reactions in polymer/monomer mixtures particularly by analytical and preparative HPLC. Poly(1,2,2,2-tetrachloroethyl methacrylate) (PTCEMA) was used as polymer while p-cumylphenythacrylate (CUPMA) was mainly added as monomer. The substances were irradiated with γ-doses up to 160 kGy. The electron beam doses at an acceleration voltage of 30 kV corresponded to this value.With the HPLC method a CUPMA-grafted PTCEMA and CUPMA oligomers were detected. UV and ¹H-NMR spectra of these separated substances obtained by preparative HPLC confirmed the formation of a graft polymer. IR and Cl-elementary analyses revealed a Cl-substitution in CUPMA oligomers. Evidently, the conversion of unsaturated monomers is decisively determined by the radiation-chemical behaviour of the polymer.     

Kinetics of formation of polybisbenzimidazobenzophenanthroline-dione (BBB polymer)

The kinetics of the polycondensation of 3,3′-diaminobenzidine with 1,4,5,8-naphthalenetetracarboxylic acid (NTC) have been investigated. Polymerizations were carried out in solution in either polyphosphoric acid (PPA) or in PPA mixed with some sulfuric acid. The reaction is heterogeneous in PPA owing to partial solubility of NTC, whereas it is homogeneous in the mixed solvent. The rate of disappearance of NTC and of dicarboxylic endgroups on oligomers was followed as a function of time at several reaction temperatures. The results show that NTC is more reactive than oligomers, so that the principle of equal reactivity is not valid for the initial steps in the polycondensation reaction.     

Thermal polymerization of arylacetylenes: A stepwise activated monomer mechanism

Kinetics of the thermal polymerization of ATR(acetylene-terminated resin) model compounds, bisphenol A monobenzyl mono(ethynylaryl) ethers, was studied by means of GPC and the resulting oligomers were characterized by FTiR, UV, and H¹ NMR techniques. It was found that monomer was consumed rapidly at first, and later slowly, yielding a mixture of dimer, low oligomers (DP ⩽ 6) and higher ones. The concentrations of every lower species remained nearly constant throughout the polymerization (except first ten minutes). In order to account for these results, a new mechanism involving the activation of monomer and its attack on the end unit of the polymer chain was proposed. This is the first example of activated monomer mechanism (a. m. mechanism) for non-catalyzed polymerization of unsaturated monomers and, at the same time, the first example of stepwise a. m. mechanism. The structure of the resulting polymer will be discussed on the basis of this mechanism.     

Poly(β-amino acid)s. IV. Synthesis and conformational properties of poly(α-isobutyl-L-aspartate)

Poly(α-isobutyl-L -aspartate) was prepared by the polycondensation reaction of p-nitrophenyl ester of α-isobutyl-L -aspartate and the conformation of the poly(β-amino acid) was investigated by X-ray diffraction, polarized infrared, circular dichroism (CD), optical rotatory dispersion (ORD), and NMR spectroscopy. α-Isobutyl β-p-nitrophenyl-L -aspartate hydrochloride and hydrobromide were used as monomers and dimethylformamide, chloroform, and chlorobenzene, as solvents. A high-molecular-weight polymer with [η] 1.0 dl/g (dichloroacetic acid, 25°C) was formed in the polymerization of the hydrochloride in chloroform at 25°C. The X-ray diagram and polarized infrared spectrum of the stretched polymer film obtained from a chloroform solution suggested a cross-β-form as the most probable structure in the solid state. The CD spectra of the polymer in a 2,2,2-trifluoroethanol (TFE) solution and its film cast from the solution showed a peak at 205 nm and a trough at 190 nm which were assigned to a β-structure. The polymer was associated in chloroform. The NMR and ORD spectra in chloroform were similar to those in TFE, which suggests that the polymer also exists in the β-structure in chloroform. The addition of small amounts of dichloroacetic acid and sulfuric acid to chloroform and TFE solutions, respectively, destroyed the β-structure. A random copolymer of α-isobutyl-L -aspartate with β-alanine was also prepared by polycondensation reaction. The copolymer apparently did not form an ordered structure in the solid state or in solution.     

Synthesis of pyrrolidine-based oxy-peptide nucleic acids carrying four types of nucleobases and their transport into cytoplasm

We synthesized 16 pyrrolidine-based oxy-peptide nucleic acid (POPNA) monomers carrying four different nucleobases onto four different stereoisomers of pyrrolidine rings. Using these monomers, we prepared POPNA oligomers, which formed sequence-specific hybrids with DNAs. The oligomer configurations influenced the hybrid stability. The oligomers were not taken into CHO cells. However, they could enter the cell cytoplasm when mixed with the influenza virus hemagglutinin peptide-arginine heptamer conjugate.     

Approaches to novel AB heteroaromatic polyamides based on cyanoimidazoles

We report the synthesis of several AB monomers based on 2-amino-4,5-dicyanoimidazole. Polymerization of the monomers to poly(imidazoleamide)s, by several methods is described. Amino acids 2-amino-4-cyano-1-methyl-5-imidazolecarboxylic acid and 2-amino-5-cyano-1-methyl-4-imidazolecarboxylic acid were prepared by mono-ethanolysis of 2-amino-4,5-dicyanoimidazole followed by methylation of the 1-nitrogen. The resulting regioisomeric mixture of ethyl esters was separated by fractional crystallization and hydrolyzed to the desired amino acids. The regioisomeric structure was determined by NOE studies of the decarboxylated amino acids. The corresponding acid chlorides were prepared with thionyl chloride and isolated as the HCl salts. Activated esters were prepared by reacting the acid chlorides with alcohols such as 1,1,1-trifluoroethanol and 2-chlorophenol. Model compounds were prepared by the acylation of aminocyanoimidazoles but yields were low. The low nucleophilicity of the aminocyanoimidazolecarboxylic acids was partially overcome by the use of the acylation catalyst 4-dimethylaminopyridine (DMAP) and the activating agent silicon tetrachloride. The acid chlorides were polymerized in amide solvents such as hexamethyl phosphoramide with pyridine and DMAP. A copolyamide consisting of both regioisomers was prepared from a regioisomeric mixture of the acid chlorides. In addition, aminolysis of 2-chlorophenyl 2-amino-4-cyano-1-methyl-5-imidazolecarboxylate resulted in a low yield of poly(imidazoleamide). Poly(imidazoleamide)s were red to tan which suggest conjugation along the polymer backbone. The solubility of the polyamides varied from amide solvents to sulfuric acid depending on the regioisomeric structure and molecular weight. The molecular weight of the heteroaramids was in the range from 1500 to 4000 based on viscosity measurements in sulfuric acid. The poly(imidazoleamide)s were thermally stable in excess of 300°C under air and nitrogen atmosphere. © 1993 John Wiley & Sons, Inc.     

Summary of findings from the Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI): corn stover pretreatment

The Biomass Refining Consortium for Applied Fundamentals and Innovation, with members from Auburn University, Dartmouth College, Michigan State University, the National Renewable Energy Laboratory, Purdue University, Texas A&M University, the University of British Columbia, and the University of California at Riverside, has developed comparative data on the conversion of corn stover to sugars by several leading pretreatment technologies. These technologies include ammonia fiber expansion pretreatment, ammonia recycle percolation pretreatment, dilute sulfuric acid pretreatment, flowthrough pretreatment (hot water or dilute acid), lime pretreatment, controlled pH hot water pretreatment, and sulfur dioxide steam explosion pretreatment. Over the course of two separate USDA- and DOE-funded projects, these pretreatment technologies were applied to two different corn stover batches, followed by enzymatic hydrolysis of the remaining solids from each pretreatment technology using identical enzyme preparations, enzyme loadings, and enzymatic hydrolysis assays. Identical analytical methods and a consistent material balance methodology were employed to develop comparative sugar yield data for each pretreatment and subsequent enzymatic hydrolysis. Although there were differences in the profiles of sugar release, with the more acidic pretreatments releasing more xylose directly in the pretreatment step than the alkaline pretreatments, the overall glucose and xylose yields (monomers + oligomers) from combined pretreatment and enzymatic hydrolysis process steps were very similar for all of these leading pretreatment technologies. Some of the water-only and alkaline pretreatment technologies resulted in significant amounts of residual xylose oligomers still remaining after enzymatic hydrolysis that may require specialized enzyme preparations to fully convert xylose oligomers to monomers.     

Solid-Phase Synthesis of Phenylacetylene Oligomers Utilizing a Novel 3-Propyl-3-(benzyl-supported) Triazene Linkage

Sequence-specific phenylacetylene oligomers consisting of functionalized monomers (hexyl benzoate, hexyl phenyl ether, benzonitrile, and tert-butylphenyl) are synthesized in gram quantities using solid-phase methods. Growing oligomers are attached to a divinylbenzene cross-linked polystyrene support by the 1-aryl-3-propyl-3-(benzyl-supported) triazene moiety. This linkage is obtained by reaction of arenediazonium tetrafluoroborate salts with a n-propylamino-modified Merrifield resin. Condensation strategies are described, producing oligomers with higher yields and simplified procedures compared to solution-phase methods. Terminal acetylene is protected with a trimethylsilyl group. After deprotection of the resin-bound terminal acetylene, an aryl iodide monomer or an aryl iodide-terminated oligomer is coupled to the supported oligomer using a palladium(0) catalyst. The cycle can be repeated to produce sequence-specific oligomers of varying length and functionality. The resulting oligomers are liberated from the polymer support by cleavage of the 1-aryl-3-propyl-3-(benzyl-supported) triazene group by reaction with iodomethane producing an aryl iodide.     

Toward large tubular helices based on the polymerization of tri(benzamide)s

Herein we present the synthesis and polycondensation of mono‐ and di‐N‐protected, bis‐substituted tri(benzamide)s with the aim to create large, tubular helices. We synthesized 2,4‐dimethoxy and 2,5‐bis‐TEGylated aminobenzoic acid derivatives as bent and linear monomers and introduced p‐methoxybenzyl (PMB) amide protecting groups to the oligobenzamide backbone. An iterative coupling strategy allowed for sequence control, giving rise to oligomers consisting of one bent and two linear monomers. The resulting meta‐para‐para‐linked aromatic trimers carried either one or two PMB‐protecting groups. With high organosolubility and flexibility, this synthetic strategy generated suitable precursors for subsequent polycondensation reactions. After polymerization, treatment with acid triggered the cleavage of the N‐protecting groups. We hypothesize that the hydrogen bonding pattern generated along the polyaramide backbone could lead to the formation of a helical polymer. A drastic change in hydrodynamic volume was observed by gel permeation chromatography and dissolution in a chiral solvent lead to the observation of a circular dichroism signal for this polymer. The results of the polycondensations of N‐protected oligobenzamides are reported herein. The formation of macrocycles as well as polymers could also be observed, giving a highly interesting insight into the underlying mechanism of the polycondensation of flexible, oligobenzamide‐based oligomers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1731–1741     

Crosslinked poly(ester anhydride)s based on poly(ε‐caprolactone) and polylactide oligomers

Resorbable poly(ester anhydride) networks based on ε‐caprolactone, L ‐lactide, and D,L ‐lactide oligomers were synthesized. The ring‐opening polymerization of the monomers yielded hydroxyl telechelic oligomers, which were end‐functionalized with succinic anhydride and reacted with methacrylic anhydride to yield dimethacrylated oligomers containing anhydride bonds. The degree of substitution, determined by ¹³C NMR, was over 85% for acid functionalization and over 90% for methacrylation. The crosslinking of the oligomers was carried out thermally with dibenzoyl peroxide at 120 °C, leading to polymer networks with glass‐transition temperatures about 10 °C higher than those of the constituent oligomers. In vitro degradation tests, in a phosphate buffer solution (pH 7.0) at 37 °C, revealed a rapid degradation of the networks. Crosslinked polymers based on lactides exhibited high water absorption and complete mass loss in 4 days. In ε‐caprolactone‐based networks, the length of the constituent oligomer determined the degradation: PCL5‐AH, formed from longer poly(ε‐caprolactone) (PCL) blocks, lost only 40% of its mass in 2 weeks, whereas PCL10‐AH, composed of shorter PCL blocks, completely degraded in 2 days. The degradation of PCL10‐AH showed characteristics of surface erosion, as the dimensions of the specimens decreased steadily and, according to Fourier transform infrared, labile anhydride bonds were still present after 90% mass loss. © 2003 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3788–3797, 2003