Polyols production by chemical modification of autocatalyzed ethanol‐water lignin from Betula alnoides

Betula alnoides lignin, recovered as a byproduct in autocatalyzed ethanol‐water pulping process, was converted into viscous polyether polyols through oxypropylation and liquefaction methods, with the aim of adding value to this byproduct. The oxypropylation reaction was performed by reacting autocatalyzed ethanol‐water lignin (AEL) with propylene oxide under the acidic and alkaline conditions at room temperature, respectively. In contrast, the liquefaction reaction was carried out using the mixed solvents of polyethylene glycol and glycerol at 160°C with sulfuric acid as a catalyst. The resulting polyether polyols from each method was characterized by Fourier transform‐infrared (FTIR), ¹H and ³¹P nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and thermogravimetric analysis. Quantitative ³¹P NMR indicated that all the aliphatic hydroxyl group values of polyols increased significantly by the above two methods. More secondary hydroxyl groups (2.016 mmol/g) were obtained in the alkaline oxypropylation reaction, whereas more primary hydroxyl groups (4.296 mmol/g) were found in the liquefied product. GPC analysis showed that the alkaline oxypropylated product (M_w 3130 g/mol, M_n 2080 g/mol) and liquefied product (M_w 4990 g/mol, M_n 4630 g/mol) have higher molecular weights than AEL (M_w 2560 g/mol, M_n 1530 g/mol). Thermal stability analysis suggested that the polyether polyols have a lower degradation temperature than AEL. These polyols used as precursors in polyurethane synthesis give promising properties, which open new avenues of exploitation of AEL. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

离子液体与水混合溶剂应用于微晶纤维素溶剂液化研究

将离子液体氯化1-丁基-3-甲基咪唑（[BMIM]C1）、水、固体酸催化剂组成的混合溶剂应用于微晶纤维素的预处理过程中,并尝试把经过预处理的微晶纤维素应用于随后的溶剂液化的研究中,对经过混合溶剂处理后的微晶纤维素进行表征分析。通过测定纤维素的聚合度、官能团基变化、热重分析、结晶结构和表面结构等对微晶纤维素结构进行比较分析。通过对苯酚溶剂液化的基本表征、残渣物的结晶结构以及生成物相对分子质量的变化了解了混合溶剂对微晶纤维素的处理效果。结果表明,通过混合离子液体[BMIM]C1和水并且添加固体酸催化剂形成新的混合溶剂体系对微晶纤维素进行预处理,发现溶剂在保留纤维素主要葡萄糖单元的同时能够有效地降低聚合度。聚合度从未处理时的190降到样品[B]C1（10）的165和样品[B]C1（10）＋NR50的151。混合溶剂对非结晶或低结晶物质具有一定的溶解能力,并且对高结晶性纤维素部分的氢键结构起到破坏作用和造成整体结晶结构的歪曲。在随后的液化过程中,处理后的纤维素液化效率有所提高,在反应2min时,固体酸加混合溶剂处理的微晶纤维素液化残渣率为19％,而未处理的液化残渣率29％。表明使用了混合溶剂添加固体酸的溶剂体系对加速液化的效果更佳,预处理对最终液化生成物的性质影响不大。     

Factors influencing molecular weights of methylcelluloses prepared from annual plants and juvenile eucalyptus

We studied the factors that influenced the molecular weights (M_w) of water‐soluble methylcelluloses prepared from annual plants and juvenile eucalyptus. Miscanthus and cardoon stalks, and bleached pulps of abaca, jute, sisal, hemp, and flax were the annual plant materials studied. A higher concentration of NaOH solution during the impregnation led to a spring cardoon methylcellulose having a lower molecular weight. As the impregnation times increased, so did the molecular weights of the water‐soluble methylcelluloses of spring cardoon. The impregnation conditions had less influence on the methylcelluloses of summer cardoon than on the methylcelluloses of spring cardoon. As the cooking times increased, so did the molecular weights of miscanthus methylcelluloses. A lower pulping severity increased the molecular weight of eucalyptus methylcellulose. The preliminary treatments (water soaking, premercerization, mercerization under pressure, and steam explosion) improved the molecular weights of water‐soluble abaca methylcelluloses. The steam explosion method was the best of the preliminary treatments for the abaca pulp. Different species led to different molecular weights for methylcelluloses synthesized from ECF bleached pulps, and these were further improved by preliminary mercerization. The molecular weight of α‐cellulose methylcellulose changed as the ratio of the methylation reagent was varied. To synthesize an optimum M_w of methylcellulose, the different raw materials can be chosen, the pulping parameters adjusted (including impregnation and cooking), the cellulose pretreated, and the methylcellulose conditions changed. The plant species is the decisive factor for the M_w of methylcellulose. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1785–1793, 2006     

Graft copolymerization of acrylic acid onto cellulose: Effects of pretreatments and crosslinking agent

The graft copolymerization of acrylic acid (AA) and 2‐acrylamido 2‐methylpropane sulfonic acid (AASO₃H) onto cellulose, in the presence or absence of crosslinking agent N,N′‐methylene bisacrylamide (NMBA), by using different concentrations of ceric ammonium nitrate (CAN) initiator in aqueous nitric acid solution at either 5 or 30°C was investigated. To investigate the effect of pretreatment of cellulose on the copolymerization, before some grafting reactions cellulose was pretreated with either 2 or 20 wt % NaOH solutions or heated in distilled water/aqueous nitric acid (2.5 × 10^?3 M) at 55°C. To determine how the excess of initiator affects the grafting and homopolymerization, separate reactions were carried out by removing the excess of ceric ions by filtration of the mixture of initiator solution and cellulose before the monomer addition. Extraction‐purified products were characterized by grafting percentage and equilibrium swelling capacity. Pretreatment of cellulose with NaOH solutions decreased the grafting percentage of copolymers. In the case of AA–AASO₃H mixtures, nonpretreated cellulose gave a higher grafting percentage than NaOH‐pretreated cellulose. Filtration also lowered the grafting of AA on the cellulose in the cases of pretreatment with either water or nitric acid. Copolymers with the highest grafting percentage (64.8%) and equilibrium swelling value (105 g H₂O/g copolymer) were obtained in grafting reactions carried out in the presence of NMBA at 5°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2267–2272, 2001     

Preparation and characteristics of polyurethane made with polyhydric alcohol‐liquefied rice husk

The limited availability of fossil resource is causing the urgent need to get renewable chemicals. Solvent liquefaction can convert rice husk into bio‐based chemicals. Rice husk was liquefied in polyhydric alcohol catalyzed by sulfuric acid under atmospheric pressure. The viscosity, residue content, and weight average molecular weight (M_w) of liquefied rice husk were 3089 cps, 23.6% and 4100, respectively. Prolonging the liquefaction time decreased the residue content and increased the average molecular weight. Polyurethane (PU) foams were successfully prepared from the liquefied rice husk with different molar ratios of NCO to OH (NCO/OH). The mechanical properties of PU foams showed that the compressive strength in the vertical direction is higher than that in the horizontal direction. With Increase of the NCO/OH molar ratio from 1.0 to 2.0, compressive strength in the vertical direction of PU foams increased from 70.6 to 114.7 kPa at 10% strain. Thermal analysis results showed that thermal stability of liquefied rice husk‐based PU resins was better than that of fossil‐ and liquefied wood‐ based PU resins. Increasing the NCO/OH molar ratio and inorganic residue of rice husk can help to increase thermal stability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45910.     

Solid‐state polymerization of poly(ethylene terephthalate): Effect of organoclay concentration

Poly(ethylene terephthalate) (PET)/Cloisite 30B (C30B) nanocomposites of different organoclay concentrations were prepared using a water‐assisted extrusion process. The reduction of the molecular weight (M_w) of the PET matrix, caused by hydrolysis during water‐assisted extrusion, was compensated by subsequent solid‐state polymerization (SSP). Viscometry, titration, rheological, and dynamic scanning calorimetry measurements were used to analyze the samples from SSP. The weight‐average molecular weight (M_w) of PET increased significantly through SSP. PET nanocomposites exhibited solid‐like rheological behavior, and the complex viscosity at high frequencies was scaled with the M_w of PET. The Maron–Pierce model was used to evaluate the M_w of PET in the nanocomposites before and after SSP. It was found that the extent and the rate of the SSP reaction in nanocomposites were lower than those for the neat PETs, due to the barrier effect of clay platelets. Consequently, the SSP rate of PET increased with decreasing particle size for the neat PET and PET nanocomposites. The effect of the M_w of PET on the crystallization temperature, crystallinity, and the half‐time, t_½, of nonisothermal crystallization was also investigated. With increasing M_w of PET, t_½ increased, whereas T_c and X_c decreased. POLYM. ENG. SCI., 54:2925–2937, 2014. © 2014 Society of Plastics Engineers     

Synthesis and cure kinetics of liquefied wood/phenol/formaldehyde resins

Wood liquefaction was conducted at a 2/1 phenol/wood ratio in two different reactors: (1) an atmospheric three‐necked flask reactor and (2) a sealed Parr reactor. The liquefied wood mixture (liquefied wood, unreacted phenol, and wood residue) was further condensed with formaldehyde under acidic conditions to synthesize two novolac‐type liquefied wood/phenol/formaldehyde (LWPF) resins: LWPF1 (the atmospheric reactor) and LWPF2 (the sealed reactor). The LWPF1 resin had a higher solid content and higher molecular weight than the LWPF2 resin. The cure kinetic mechanisms of the LWPF resins were investigated with dynamic and isothermal differential scanning calorimetry (DSC). The isothermal DSC data indicated that the cure reactions of both resins followed an autocatalytic mechanism. The activation energies of the liquefied wood resins were close to that of a reported lignin–phenol–formaldehyde resin but were higher than that of a typical phenol formaldehyde resin. The two liquefied wood resins followed similar cure kinetics; however, the LWPF1 resin had a higher activation energy for rate constant k₁ and a lower activation energy for rate constant k₂ than LWPF2. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Liquefaction of cellulose in the presence of phenol using p-toluene sulfonic acid as a catalyst

The kinetics of p-toluene sulfonic acid (PTSA)-catalyzed cellulose liquefaction in the presence of phenol were investigated at 130, 140 and 150 °C. The resulting liquefied products were also analyzed to evaluate the effectiveness of PTSA as a catalyst during the phenol liquefaction. The liquefaction rate of PTSA was slightly lower than that of sulfuric acid (SA), which was used as a reference catalyst, at each liquefaction temperature. The activation energies of the PTSA and SA catalysts during the phenol liquefaction of cellulose calculated using the Arrhenius equation were 34.5 and 35.5 kcal/mol, respectively. The chemical compositions of the ether extracts in the liquefied products were very similar to both catalysts. Methylene bisphenol and its isomers, which were the primary components in the ether extracts, comprise approximately 30% of the ether extract. The GPC curves of the 80% dioxane-soluble part of the liquefied product indicated that it consists of a remarkable amount of phenol-based trimers to hexomers. The average molecular weight and the polydispersity of the liquefied products were very similar after liquefaction using both catalysts; therefore, differences in the products produced using both catalysts used were not recognized. However the level of combined phenol in the liquefied product produced using the PTSA catalyst was approximately 50% lower than that of the SA catalyst. Although it is believed that this difference may cause retardation of the rate of liquefaction, further experiments are necessary to explain differences in the effectiveness of organic sulfonic acid catalysts during the phenol liquefaction of lignocellulosic biomass.     

Poly‐2‐[(4‐methylbenzylidene)amino]phenol: Investigation of thermal degradation and antimicrobial properties

A new polyphenol (poly‐2‐[(4‐methylbenzylidene)amino]phenol) (P(2‐MBAP)) containing an azomethine group was synthesized by oxidative polycondensation reaction of 2‐[(4‐methylbenzylidene)amino]phenol (2‐MBAP) with NaOCl, H₂O₂, and O₂ oxidants in an aqueous alkaline medium. The structures of 2‐MBAP and P(2‐MBAP) were characterized by UV‐vis, FT‐IR, and ¹H NMR spectra. While the monomer decomposed completely up to 350°C and 57.2% of the polymer decomposed up to 1000°C. The thermal degradation of P(2‐MBAP) was also supported by the Thermo‐IR spectra recorded in the temperature range of 25–800°C. Electrical conductivity of the polymer was observed to increase 10⁸ fold after doping with I₂. Antimicrobial activities of the P(2‐MBAP) and 2‐MBAP against Sarcina lutea, Enterobacter aerogenes, Escherichia coli, Enterococcus feacalis, Klebsiella pneumoniae, Bacillus subtilis, Candida albicans, and Saccharomyces cerevisiae were also investigated. The number average molecular weight (M_n), weight average molecular weight (M_w) and polydispersity index (PDI) of the polymers were determined by gel permeation chromatography (GPC). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41758.     

Polyurethane foams made from liquefied bark‐based polyols

Liquefaction is known to be an effective method for converting biomass into a polyol. However, the relationships between bark liquefaction conditions and properties of the resulting foams are unclear. In this study, polyurethane foams (PUF) were made using bark‐based polyols obtained through liquefaction reactions of bark at two different temperatures (90 and 130°C). Through systematic characterization of the PUFs the influence of the liquefied bark and liquefaction conditions on foam properties could be observed. The bark‐based foams had similar foaming kinetics, thermal stability, and glass transition temperatures compared with the PEG‐based control foam. The bark‐based PUF from the polyol obtained at the higher liquefaction temperature showed comparable specific compressive strength to the PEG‐based control foam. Lastly, both bark foams exhibited a high amount of open‐cell content, with the foam made from the lower temperature liquefied polyol having poor cell morphology. This deviation from the controls in the open‐cell content may explain the lower modulus values observed in the bark PUFs due to the lack of cell membrane elastic stretching as a strengthening mechanism. These results demonstrated the influence of the bark liquefaction conditions on foam properties, thereby providing a better fundamental understanding for the practical application of bark‐based PUFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40599.     

Properties of phenol‐formaldehyde resins prepared from phenol‐liquefied lignin

In this study, alkaline lignin (AL), dealkaline lignin (DAL), and lignin sulfonate (SL) were liquefied in phenol with sulfuric acid (H₂SO₄) or hydrochloric acid (HCl) as the catalyst. The phenol‐liquefied lignins were used as raw materials to prepare resol‐type phenol‐formaldehyde resins (PF) by reacting with formalin under alkaline conditions. The results show that phenol‐liquefied lignin‐based PF resins had shorter gel time at 135°C and had lower exothermic peak temperature during DSC heat‐scanning than that of normal PF resin. The thermo‐degradation of cured phenol‐liquefied lignin‐based PF resins was divided into four temperature regions, similar to the normal PF resin. When phenol‐liquefied lignin‐based PF resins were used for manufacturing plywood, most of them had the dry, warm water soaked, and repetitive boiling water soaked bonding strength fitting in the request of CNS 1349 standard for Type 1 plywood. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of new novolacs based on heteroatom‐bridged phenol derivatives

We describe the synthesis and properties of new novolacs prepared by addition‐condensation of heteroatom‐bridged phenol derivatives and formaldehyde. The trifluoroacetic acid‐catalyzed polymerization of equimolar amounts of bis(4‐methoxyphenyl) ether ( 1a ) and formaldehyde proceeded homogeneously to afford the polymer ( 2a ) in 49% yield (M_n 2600, M_w/M_n 1.8). From the FTIR, ¹H‐NMR, and ¹³C‐NMR spectra of 2a , it was evident that the polymer had methylene moieties‐bridged repeating units in the polymer backbone. A higher molecular weight novolac ( 2a ′) (yield 99%, M_n 16,600, M_w/M_n 12.9) could be prepared by using an excess of formaldehyde. Bis(4‐methoxyphenyl) sulfone novolac ( 2b ) (M_n 1300, M_w/M_n 1.2) and bis(4‐methoxyphenyl) sulfide novolac ( 2d ) (M_n 1200, M_w/M_n 1.9) were also prepared. However, the polymerization of bis(4‐hydroxyphenyl) sulfone ( 1c ) did not proceed, even when it was attempted under various reaction conditions. From TGA, the temperatures at 10% loss in weight (T₁₀) for 2a , 2a ′, and 2b were found to be 413, 430 and 393°C, respectively. These results suggested that heteroatom‐bridged novolacs based on phenol derivatives have good thermal stability than other organosoluble polymers; moreover, these novolacs could be expected to function as processable materials, polymer blends for engineering plastics, etc. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A novel route for green conversion of cellulose to HMF by cascading enzymatic and chemical reactions

In this work, a novel route to deconstruct cellulose into 5‐hydroxymethylfurfural (HMF) by cascading enzymatic and chemical reactions is reported. For biocatalyst preparation, Fe₃O₄ nanoparticles encapsulated SBA‐15 with appropriate pore size was synthesized and utilized as magnetic scaffolds for the immobilization of cellulase. For chemical catalyst preparation, sulfated zirconium dioxide conformed monolayers were grafted on SBA‐15 template to create thermally robust mesoporous catalysts with tunable solid basic/Lewis acid and Brønsted acid sites. Catalytic performance of biocatalyst and chemical catalyst was explored in the aqueous phase conversion of IL pretreated cellulose to glucose, and in the iPrOH/water solvent conversion of glucose to HMF conversion, respectively. After the optimization of reaction conditions, a sequential conversion of pretreated cellulose to glucose and glucose to HMF was performed, and 43.6% HMF yield can be obtained. The cascaded enzymatic and chemocatalytic reaction system demonstrates an effective and economically friendly process for biomass energy conservation. A novel route for green conversion of IL pretreated cellulose to 5‐hydroxymethylfurfural (HMF) by cascading an enzymatic catalysis in an aqueous system with chemocatalysis in an iPrOH/water solvent mixture is reported. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Characterization of liquefied wood residues from different liquefaction conditions

The amount of wood residue is used as a measurement of the extent of wood liquefaction. Characterization of the residue from wood liquefaction provides a new approach to understand some fundamental aspects of the liquefaction reaction. Residues were characterized by wet chemical analyses, Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM). The Klason lignin content of the residues decreased, while the holocellulose and α‐cellulose contents increased as the phenol to wood ratio (P/W) increased. A peak at 1735 cm^?1, which was attributed to the ester carbonyl group in xylan, disappeared in the FTIR spectra of the residues from liquefied wood under a sealed reaction system, indicating significantly different effects of atmospheric versus sealed liquefaction. The crystallinity index of the residues was higher than that of the untreated wood particles and slightly increased with an increase in the P/W ratio. The SEM images of the residues showed that the fiber bundles were reduced to small‐sized bundles or even single fibers as the P/W ratio increased from 1/1 to 3/1, which indicated that the lignin in the middle lamella had been dissolved prior to the cellulose during liquefaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Polyurethane coatings from liquefied wood containing remains of a copper‐, chromium‐, and boron‐based wood preservative

Preparation of polyurethane wood coatings based on copper‐, chromium‐, and boron (CCB) containing liquefied wood was performed, as an alternative way to manage postconsumed preservative‐contaminated wood. Additionally, we examined the possibility of improvement of selected properties of the liquefied wood‐based coatings by an addition of silica nanoparticles. The constituents of the CCB wood preservative do not exhibit an influence on a liquefaction process and on composition of the liquefied mixture. CCB also does not affect curing of the formulations containing liquefied wood and an isocyanate‐type hardener. Furthermore, influence of CCB on adhesion strength of liquefied wood‐based coatings on a wooden substrate, their hardness, and resistance to scratching and to water, acetone, and alcohol, is not exhibited. However, apart from these, from the applicative point of view, positive results, any improvement of the coating properties by the addition of silica nanoparticles is not shown. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40865.     

Polyols and polyurethane foams from acid‐catalyzed biomass liquefaction by crude glycerol: Effects of crude glycerol impurities

The effects of crude glycerol impurities on acid‐catalyzed biomass liquefaction by crude glycerol were investigated. Salts (i.e., NaCl and Na₂SO₄) decreased biomass conversion ratios and negatively affected the properties of polyols produced. Regression models were developed and validated as appropriate for describing the relationships between organic impurities and biomass conversion ratios and between organic impurities and the hydroxyl number of polyols. Polyols produced from crude glycerol containing 0–45% organic impurities showed the hydroxyl number varying from 1301 to 700 mg KOH/g, acid number from 19 to 28 mg KOH/g, viscosity from 2.4 to 29.2 Pa s, and molecular weight (M_w) from 244 to 550 g/mol. Crude glycerol containing 40–50 wt % of organic impurities was suitable to produce polyols with suitable properties for rigid and/or semi‐rigid polyurethane (PU) foam applications. The produced PU foams showed density and compressive strength comparable to those derived from petrochemical solvent‐based liquefaction processes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40739.     

Free radical scavenging activity of cellulase‐treated chitosan

Partially N‐acetylated chitosan was hydrolyzed by the cheap, commercially available, and efficient cellulase. The products, with different molecular weight, were comparatively investigated by GPC, FT‐IR, XRD, and NMR. The results show that the decrease of molecular weight led to transformation of crystal structure and increase of water‐solubility, but the chemical structures of residues were not modified. Superoxide anion radical and hydroxyl radical quenching assay were used for the evaluation of free radical scavenging activity of cellulase‐treated chitosan in vitro. Low molecular weight chitosan (LMWC3, M_w 1.7 × 10³) exhibited high scavenging activity against free radical. It scavenged 79.3% superoxide radical at 0.1 mg mL^?1. At 2.0 mg mL^?1, scavenging percentage of initial chitiosan, LMWC1 (M_w 27.3 × 10³), LMWC2 (M_w 5.9 × 10³), and LMWC3 (M_w 1.7 × 10³) against hydroxyl radical was 14.3%, 33.1%, 47.4%, and 65.9%, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of crosslinking density on resilient performance of low‐resilience flexible polyurethane foams

Low‐resilience flexible polyurethane foams (FPUFs) with varying crosslinking densities, were synthesized from polyols, 4, 4′‐diphenyl methane diisocyanate (MDI‐100), and water. The effects of crosslinking agent content, the molecular weight (M_w) of polyether diol, and the ratio of (polyether triol)/(polyether diol) on the resilience performance of FPUFs were investigated. Results indicate that higher crosslinking density was beneficial to the increasing of recovery time. The recovery time of the FPUF using polyether diol with M_w of 400 was 24.3 s. It was 3.2 times longer compared with FPUF using polyether diol with M_w of 3000. Dynamic mechanical analysis (DMA) results showed that, FPUFs with high crosslinking density displayed viscoelasticity in a wider range of temperature. However, when molecular chains were longer enough, FPUFs with low crosslinking density also demonstrated significant viscoelasticity, which is owing to the excess of physical crosslinking points. The results in stress–strain cycling and recovery time experiments were consistent with the results of DMA. POLYM. ENG. SCI., 55:308–315, 2015. © 2014 Society of Plastics Engineers     

Synthesis and properties of copolymer epoxy resins prepared from copolymerization of bisphenol A,epichlorohydrin, and liquefied Dendrocalamus latiflorus

Dendrocalamus latiflorus Munro (ma bamboo) was liquefied in phenol and polyhydric alcohol (polyethylene glycol/glycerol cosolvent) with H₂SO₄ as catalyst. Liquefied bamboos reacted with bisphenol A and epichlorohydrin were then employed to prepare copolymer epoxy resins. The curing property and thermal property of copolymer epoxy resins were investigated. The results showed that copolymer epoxy resins could cure at room temperature after the hardener was added, and its curing process was an exothermic reaction. Comparison showed that copolymer epoxy resins prepared with phenol‐liquefied bamboo as raw material had higher heat released than those prepared with polyhydric alcohol‐liquefied bamboo during curing. The DSC analysis showed that heat treatment could enhance the crosslinking of copolymer epoxy resins cured at room temperature. However, resins prepared with polyhydric alcohol‐liquefied bamboo had a lower glass transition temperature. The TGA analysis showed that resins prepared with phenol‐liquefied bamboo had better thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Low molecular weight water‐soluble chitosans: Preparation with the aid of cellulase,characterization, and solubility

Preparation of water‐soluble chitosan (WSC) was made by treating partially N‐deacetylated chitosan with acetic anhydride in aqueous acetic acid. The optimal conditions of preparing WSC were determined on the basis of orthogonal tests. Low molecular weight WSC with broad molecular weight (600–1.5 kDa) were obtained by the depolymerization of WSC using cellulase at optimum condition of pH 4.5 and 60°C. The solubility of WSC in water and aqueous organic solvents was investigated in detail. Weight–average molecular weight (M_w) and molecular weight distribution (M_w/M_n) of samples were measured by gel permeation chromatography. The structure of WSC and its degraded products were characterized by XRD, FTIR, and MALDI‐TOF MS. The decrease of molecular weight led to transformation of crystal structure and the increase of solubility, but the chemical structures of residues were not modified compared to WSC, which was not hydrolyzed. The solubility of the WSC in water and aqueous organic solvents increased with the decrease of molecular weight. The solubility of the WSC with low molecular weight was rather high even in aqueous dimethylacetamide and dimethylsulfoxide. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1098–1105, 2006