Carbohydrate stabilization with anthraquinone during alkaline pulping

Summary Treatment of wood meal with aqueous alkali in the presence of anthraquinone at 80°C leads to a conversion of reducing hexose end groups in the polysaccharides to mannonic and gluconic acid end groups. Xylose end groups are oxidized to xylonic and lyxonic acid groups. This leads to a stabilization of the polysaccharides against endwise alkaline degradation.     

The Role of Carbohydrates in Alkali Anthraqutnone Pulping

The reactions of carbohydrates with anthraquinones in alkaline pulping processes are reviewed. AQ reacts mainly with the short-lived intermediates that are formed in the degradation reactions of wood polysaccharides. Oxidation of the reducing end groups of polysaccharides to stable aldonic acid end groups is marginal and corresponds to less than 1 % of all reactions of AQ. The stabilization of the polysaccharides may be enhanced by the use of salts of alkaline earth metals which increase the relative oxidation rate of sugar enediols and promote the hydride shift reaction of the intermediate aldos-2-ulose end groups to stable hexonic acid end groups. Analysis of the monomeric carbohydrate-derived oxidation products indicates that hardwood lignin probably contains more structures that react with anthrahydroquinone than does softwood lignin. This difference may partly explain the more facile delignification of hardwoods.     

End-wise degradation of hydrocellulose during hot alkali treatment

Determinations of reducing and carboxylic acid end groups in hydrocellulose treated with hot alkali showed that the end-wise degradation proceeded to such an extent that some of the molecules were brought completely into solution. The major carboxylic acid end groups formed in reactions competing with the end-wise degradation were 3-deoxyhexonic and 2-C-methylglyceric acids; but 2-deoxypentonic, 2-C-methylpentonic, and minor amounts of aldonic acids were also formed. The formation of these stable end groups explains the observed increase in number average degree of polymerization during the treatment. The ratio between the number of lost glucose moieties and the number of carboxylic acid groups formed in the solid phase was about 170 and was only slightly affected by the duration of the hot alkali treatment.     

Effect of boric acid on the stabilization of poly(acrylonitrile-co-itaconic acid)

The effect of boric acid on the stabilization of poly(acrylonitrile-co-itaconic acid) (P(AN-co-IA)) was studied in detail by differential scanning calorimetry (DSC) incorporating with thermogravimetry (TG) in air and nitrogen. In nitrogen atmosphere the ionic cyclization of the doped P(AN-co-IA) copolymer was badly retarded by boric acid, however, the free radical cyclization was little influenced. In air atmosphere boric acid was found to weaken the first exothermic peak corresponding to dehydrogenation and cyclization reactions, and enhance the second exothermic peak corresponding to the oxidative reactions resulting in a great expansion of the heat evolved. The activation energy of stabilization was calculated with Kissinger method, the results indicated that boric acid seemed to be effective to reduce the activation energy. TG studies showed that boric acid could reduce the weight loss during stabilization, which could be attributed to the crosslinking of polymer chains caused by the reaction between boric acid and the hydroxyl groups.     

Synthesis and properties of novel fluoroalkyl end‐capped oligomers containing phosphorus segments

New fluoroalkyl end‐capped oligomers containing pendant phosphoric acid groups wereprepared by the reactions of the corresponding monomer with fluoroalkanoyl peroxides. It was demonstrated that not only strong aggregations of fluoroalkyl segments but also hydrogen bonding could interact synergistically to form the highly viscoelastic fluids (gel‐like fluids) in aqueous solutions of these new fluoroalkyl end‐capped oligomers containing pendant phosphoric acid groups. Furthermore, these oligomers were able to reduce the surface tension of water effectively to exhibit a clear breakpoint resembling a CMC, and the modified stainless‐steel surface treated with these oligomers was shown to possess an excellent property imparted by fluorine. More interestingly, these oligomers were found to be potent and selective inhibitors against HIV‐1 replication in vitro. New fluoroalkyl end‐capped phosphonic acid and phosphonate oligomers were also prepared by the reactions of the corresponding phosphonic acid and phosphonate monomers, respectively, by the use of fluoroalkanoyl peroxides. These new fluoroalkyl end‐capped phosphonic acid and phosphonate oligomers were found to have a higher solubility in not only water but also in common organic solvents than that of the corresponding fluorinated oligomers containing pendant phosphoric acid groups, and these new oligomers were able to reduce the surface tension of these solvents quite effectively. Thus, these oligomers are expected to develop as new fluorinated oligosurfactants. Moreover, the modified poly(methyl methacrylate) surface treated with these phosphonate oligomers was clarified to exhibit a good oil‐repellency imparted by fluorine. In addition, fluoroalkyl end‐capped phosphonate homo‐ and cooligomers were found to form monomolecular films at the air–water interface. Therefore, these fluorinated oligomers are suggested to have high potential for new functional materials through not only their excellent properties imparted by both fluorine and phosphorus, but also through their biological properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 228–245, 2001     

Synthesis, optical and electrochemical properties of new hyperbranched poly(triphenylamine amide)s

A new triphenylamine-containing AB₂ type monomer with one carboxylic acid and two amino groups, 4-(bis(4-aminophenyl)amino)benzoic acid (3), was synthesized and used for the preparation of hyperbranched poly(triphenylamine amide)s. The self-polycondensation of the AB₂ monomer (3) afforded hyperbranched poly(triphenylamine amide) with amino end groups. The molecular weight of the hyperbranched poly(triphenylamine amide) was 21,000 Da determined by light scattering. End-capped hyperbranched polyamides were isolated by the chemical modification of unreacted amino groups with various acid chlorides. All the hyperbranched poly(triphenylamine amide)s exhibit excellent solubility in organic solvents such as NMP, DMF, DMSO, and DMAc at room temperature. The viscosities of hyperbranched poly(triphenylamine amide)s are as low as about 0.15 dL/g due to their dendritic structures. Poly(triphenylamine amide)s end-capped with rigid benzene ring have higher thermal stability than those with amino or aliphatic end groups. The photoluminescence of the hyperbranched polyamides is blue-yellow emissions around 430-510 nm. The energy gaps of the hyperbranched poly(triphenylamine amide)s with different end groups are about 2.93 eV and are independent on the end groups, but the HOMO and LUMO energy levels are dependent on the end groups.     

Die Trennung von Oligomeren des Polyestertyps Diol-Monool-Dicarbonsäure

Separation of the Oligomers of Polyesters of the Type Diol-Monool-Dicarboxylic Acid The separation of oligomers of polyesters of the type diolmonool-dicarboxylic acid could be achieved by Craig's partition, column chromatography and especially thin-layer chromatography. As diol, ethylene glycol, glycerin-1-methyl ether and glycerin-2-methyl ether, as monool, octadecyl alcohol and as dicarboxylic acid, adipic and phthalic acids were used. The oligomers having the same end groups and built of polyester chains blocked on one and two sides could be separated by thin-layer chromatography. The oligomers which do not have the same end groups but otherwise the same structure could also be separated by thin-layer chromatography.     

Poly(n-butyl methacrylate) with primary amine end groups for supporting cell adhesion and proliferation of renal epithelial cells

Polymer coatings that support epithelial cell culture have been developed. Ozonolysis and subsequent workup of poly(butyl methacrylate-co-butadiene) copolymers is used to form oligomers with carboxylic acid end groups, which are then further reacted with diamines to provide poly(butyl methacrylate)s with primary amine end groups. The polymers are cast as films and used as cell culture substrates for human dermal fibroblasts and human renal epithelial cells. Fibroblast and epithelial cells adhere and proliferate on acid functional materials but on amine functional films epithelial cells show greater viability than fibroblasts.     

Effects of lead salts on thermal poly(vinyl chloride degradation)

The effect of lead salts (lead stearate, tribasic lead sulfate and tribase/stearic acid) on the thermal degradation of PVC was studied in trichlorobenzene (TCB) solution and under dynamic conditions in a mixing chamber. It was established that lead stearate directly reduces the HCl elimination rate (mainly by diminishing the zip length) whereas the tribase is acting only as HCl acceptor. In presence of stearic acid the tribase becomes a true stabilizer. At the end of the induction period rapid increase of the zip length and transiently high HCl elimination rates were observed. The consequences of these on the possible mechanism of stabilization are discussed.     

环氧脂肪酸钙的直接法合成及其对PVC的热稳定作用

以一种简便的方法制备了环氧基保留完好的高纯度环氧脂肪酸钙,研究发现环氧脂肪酸钙对聚氯乙烯（PVC）的热稳定作用类似于硬脂酸钙,具有长期热稳定性的特征;但其热稳定效能明显优于后者,且具有较好的初期着色性.     

Solid‐state polymerization of poly(ethylene terephthalate). II. Modeling study of the reaction kinetics and properties

Comprehensive modeling studies were used to describe the kinetics of the solid‐state polymerization (SSP) of poly(ethylene terephthalate). The validity of the model was confirmed by the successful fitting of the experimental results for molecular weight increases, at temperatures ranging from 180 to 230°C and for times up to 12 h, with one fitting parameter. The changes in the concentrations for hydroxyl end groups ([? OH]), carboxyl end groups ([? COOH]), vinyl end groups, and terephthalic acid (TPA) were simulated with the model. During SSP, the contents of not only hydroxyl and carboxyl end groups but also vinyl ester end groups and TPA monomer were predicted to decrease as a function of the SSP time and temperature. The effects of the pellet size and the molar ratio of carboxyl end groups to hydroxyl end groups were also calculated. At an end‐group molar ratio ([? COOH]/[? OH]) of around 0.7, a maximum SSP rate was obtained. As the [? COOH]/[? OH] ratio increased, the contents of the vinyl end groups and TPA monomer were predicted to increase. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 213–227, 2003     

Neutron reflectometry investigation of polymer-polymer reactions at the interface between immiscible polymers

Primary amine end functionalised deuteropolystyrene has been mixed with unmodified hydrogenous polystyrene and a thin film placed on top of a film of an acrylic polymer that either has carboxylic acid groups located at one end of each molecule or as substituents on each repeat unit. After holding at 453 K for defined times, the interfacial excess layer at the interface between the two polymers has been quantitatively analysed using neutron reflectometry and the extent of grafting of the deuteropolymer at the interface determined. Whilst maintaining the concentration of carboxylic acid units constant (fixed reacting groups) the extent of grafting increases with concentration of the functionalised deuteropolystyrene in the polystyrene layer. On changing the molecular weight of the functionalised deuteropolystyrene but maintaining the molar concentration of reactive end groups constant, the extent of grafting is larger for the lower molecular weight polymer. Although, the qualitative variation of the extent of grafting with time is in agreement with theories for interfacial grafting, exact correspondence cannot be obtained. The initial rate of grafting corresponds to second order rate constants of ∼0.1-0.2 l mol⁻¹ s⁻¹ but saturation of grafting is evident at far lower values (and hence earlier in the reaction process) than predicted by theory. Moreover, this saturation extent of grafting is at a level much lower than anticipated if brush-like layer formation is encouraged by interfacial grafting.     

Grafting reactions onto poly(organophosphazenes). VI. Thermooxidative stabilization of poly[bis (4-benzylphenoxy)phosphazene] by grafting acrylate polymers containing HALS groups

Poly[bist 4-benzylphenoxy phosphazene] is heated at 200 C in air and the oxidation of the 4-diphenylmethane side substituent to phosphazene-supported benzophenone, benzhydrol, and hydroperoxides is observed. The thermo-oxidative stabilization of the polymer is obtained by light-induced grafting copolymerization of the acrylic acid 2.2.6.6-tetramethyl-piperidin-4-yl ester onto the polyphosphazene substrate. The HALS moieties grafted onto the polyphosphazene films prevent the oxidative modification of the substituents and preserve the polymer against thermal damage. This process, investigated by IR. UV, and EPR spectroscopy, is basically dependent on the amount of HALS groups grafted onto the polyphosphazene matrix and on the composition of the reaction medium used to carry out the grafting process. The comparison between the thermooxidative stabilization process and the corresponding photooxidative stabilization reaction is also discussed.Presented at the 1st Italian Workshop on Cyclo- and Poly(phosphazene) Materials. Lebruary 15–16, 1996, at the CNR Research Area in Padova, Italy.     

Cerium–initiated Polymerisation of Some Vinyl Compounds in Polyamide Fibres

Several vinyl polymers have been grafted onto nylon 6. 6 with ceric salts as initiators. Some factors influencing the polymerisation of acrylic acid have been examined in detail, and evidence obtained that the products are true graft copolymers. Grafting of both 2–vinylpyridine and 4–vinylpyridine is slow from solutions in dilute sulphuric acid or nitric acid, but rapid from perchloric acid. Slow diffusion of initiator into polyamide fibres is apparently responsible for a non–uniform distribution of polymer sometimes observed. Nylon 6. 6 is oxidised slowly, but extensively, by cerie salts and the reaction is accelerated by oxygen. Analyses of the products are consistent with oxidation at methylene groups adjacent to the amide nitrogen rather than at amine end–groups. A paradox, thatdinitrophenylation renders nylon less susceptible to grafting of poly(acrylic acid), but not to oxidation by eerie salts, is tentatively explained. The surface electrical resistivity of nylon fabric is not lowered by grafted polyacrylamide or its N–alkyl derivatives, whilst salts of poly(acrylic acid) and poly(vinylpyridines) impart only a temporary lowering. Poly(1–rnethyl–4–vinylpyridinium) perchlorate was more permanently effective. Attempts to polymerise some potentially antistatic betaine–type monomers in nylon were unsuccessful.     

环氧脂肪酸钙/锌的直接合成法及其热稳定作用

以一种简便的方法制备了环氧基保留完好的高纯度环氧脂肪酸钙/锌，并对其热稳定性进行了研究。研究表明，环氧脂肪酸钙/锌对聚氯乙烯（PVC）的热稳定作用类似于硬脂酸钙/锌，但其热稳定效能明显优于后者，环氧脂肪酸钙比硬脂酸钙具有较好的初期着色性，环氧脂肪酸锌较硬脂酸锌具有较长的“锌烧”时间。     

新型固体钙锌复合稳定剂的直接法合成及其对PVC热稳定作用的研究

以一种简便的方法制备了以环氧脂肪酸钙、环氧脂肪酸锌为主的固体钙锌复合稳定剂,研究发现其对PVC不但有较好的长期热稳定作用,而且具有较好的初期着色性。可用于无毒制品,具有良好的社会效益和经济效益。     

Carboxyl-stabilized emulsion polymers

An emulsion polymerization process is reported for the production of high-solids, surfactant-free styrene/butadiene latices. With this procedure latices require no surfactants, for stabilization is built into the emulsion particles by means of copolymerized acid monomers. This “pH variable” method is a two-step, batch-on-batch polymerization. In the first step, all the ingredients are present in the reaction mixture; however, only enough styrene and butadiene is added to reach a low solids content. This step, carried out at low pH, produces a carboxylated seed latex. On raising the pH of this low-solids emulsion, the copolymerized carboxyl groups ionize, and the now highly charged latex particles provide an expedient locus for the generation of stable, highsolids latices. Neutralizing the carboxyl groups of the seed latex before adding the remaining monomers induces the highly hydrophilic carboxyl anions to remain on the surface of the latex particle, nearer to the aqueous environment of the surrounding media. Hence, the maximum stabilization capacity of the acid monomers is utilized. The process was evaluated to ascertain the effects of the following variables: the particle size and solids content of the first step, the nature of the base used to raise the pH, the pH of the dispersion prior to the second step, and the effect of the acid monomer on the latex stability.     

直接法合成环氧脂肪酸钙及其对PVC热稳定作用的研究

以一种简便的方法制备了环氧基保留完好的高纯度环氧脂肪酸钙.研究发现环氧脂肪酸钙对聚氯乙烯(PVC)的热稳定作用类似于硬脂酸钙,具有长期热稳定性的特征,但其热稳定效能明显优于后者,且具有较好的初期着色性.     

硼酸改性对聚丙烯腈纤维预氧化的影响

通过在线监测聚丙烯腈(PAN)纤维的热收缩应变和应力,研究了硼酸改性对PAN纤维预氧化的影响。试验结果表明:随着硼酸溶液浓度的增加,PAN纤维化学反应的起始和结束温度向高温方向移动,化学收缩量降低,预氧化纤维体密度逐渐降低,硼酸对PAN纤维化学反应有抑制作用;硼酸对分子内环化和分子间交联反应的抑制可有助于预氧化纤维均质化程度的提高,并可防止PAN纤维表面在较高温度下被过度氧化。     

Carbohydrate stabilization in wood by quinones and oxygen

Summary Spruce meal, impregnated with magnesium sulfate to suppress the depolymerization of the carbohydrates by oxygen, was treated with 1 M sodium hydroxide at 100°C in the presence of anthraquinone (AQ) or anthraquinone-2-sulfonic acid (AMS). A decreased loss of carbohydrates obtained in the presence of oxygen is related to an increased conversion of the reducing sugar end groups to aldonic acid end groups. Larger effects of oxygen were obtained with AMS compared to AQ.