Xiaohuan Liu

Integration of renewable cellulose and rosin towards sustainable copolymers by “grafting from” ATRP

A class of sustainable and renewable cellulose–rosin copolymers were prepared by immobilizing rosin-derived polymer chains on the backbone of ethyl cellulose (EC) by “grafting from” atom transfer radical polymerization (ATRP). Four different rosin based polymers derived from dehydroabietic acid (DA), one of the major resin acids in natural rosin, were attached to 2-bromoisobutyryl-functionalized EC. Meanwhile, DA-grafted EC was prepared by the simple esterification reaction between DA and EC. Kinetic studies showed that the polymerization of all monomers was controlled. These grafted copolymers adopt a worm-like or rod-like structure in tetrahydrofuran, verified by light scattering experiments. These copolymers have a tunable glass transition temperature and higher thermal stability in contrast to EC. Surface morphology by AFM analysis indicated good film-forming property when rosin polymers were grafted from EC. Additionally, the introduction of DA and rosin polymers remarkably enhanced the hydrophobicity of EC. The static contact angles of all these modified copolymers are above 90°. XPS analysis revealed that the surface of these rosin-modified EC copolymers was dominated by a hydrocarbon-rich rosin moiety. The UV absorption of modified EC composites is indicative of their potential application in UV-absorbent coating materials.

Integration of lignin and acrylic monomers towards grafted copolymers by free radical polymerization

Three kinds of acrylic monomers (2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA), methyl methacrylate (MMA) and butyl acrylate (BA)) were utilized to modify the lignin (BBL) by grafting from free radical polymerization (FRP), respectively. Calcium chloride/hydrogen peroxide (CaCl2/H2O2) was used as initiator. Effects of monomer type and concentration, initiator concentration and polymerization time on grafting from BBL were studied. Grafting of poly (acrylic monomers) onto BBL was verified by the following characterizations and this synthesis method was found to be high efficient and selective for grafting polymerization of BBL. The presence of the BBL moiety in the backbone also resulted in higher glass transition temperature compared with the homopolymer of each monomer, and some modified copolymers also improved its thermal stability. All modifications made BBL more hydrophobic and the static contact angles of these modified copolymers were above 80°. XPS analysis revealed that the surface of these modified BBL copolymers were dominated by acrylate monomer moiety. Additionally, the BBL-g-PBA copolymers can be used as dispersion modifiers in PLA-based materials to enhance UV absorption.

Preparation and characterization of lignin based macromonomer and its copolymers with butyl methacrylate

Copolymerization of butyl methacrylate (BMA) with biobutanol lignin (BBL) was achieved by free-radical polymerization (FRP) using a lignin-based macromonomer. The lignin-based macromonomer containing acrylic groups was prepared by reacting acryloyl chloride with biobutanol lignin using triethylamine (TEA) as absorb acid agentin. From the results of elemental analysis and GPC, the average degree of polymerization (DP) of BBL was estimated to be five. A detailed molecular characterization has been performed, including techniques such as (1)H NMR, (13)C NMR and UV-vis spectroscopies, which provided quantitative information about the composition of the copolymers. The changes in the solubility of lignin-g-poly(BMA) copolymers in ethyl ether were dependent on the length of poly(BMA) side chain. TGA analysis indicated that the lignin-containing poly(BMA) graft copolymers exhibited high thermal stability. The bulky aromatic group of lignin increased the glass-transition temperature of poly(BMA). In order to confirm the main structure of copolymer, (AC-g-BBL)-co-BMA copolymer was also synthesized by atom transfer radical polymerization (ATRP), and the results revealed that the copolymer prepared by ATRP had the same solution behavior as that prepared by FRP, and the lignin-based macromonomer showed no homopolymerizability due to the steric hindrance. In addition, the lignin-co-BMA copolymer had a surprisingly higher molecular weight than poly(BMA) under the same reaction condition, suggesting that a branched lignin based polymer could be formed.

Preparation and characterization of Lignin-graft-poly (ɛ-caprolactone) copolymers based on lignocellulosic butanol residue

In this paper, a graft from Ring-Opening Polymerization (ROP) technique was used to synthesize a lignin-graft-poly (ɛ-caprolactone) copolymer (BBL-g-PCL) using biobutanol lignin (BBL) as raw material recovered from lignocellulosic butanol residue. Polymerizations were carried out with various mass ratios of BBL and CL monomer ([BBL]/([BBL]+[CL])=1.0%, 5.0%, 10%, 20% and 40% (w/w)) to obtain BBL-g-PCL copolymers with different molecular weights, ranging from 367 to 8163gmol(-1). The grafting efficiency was preliminary evidenced by the long-term stability of dissolution of BBL-g-PCL in toluene. FT-IR and NMR analysis provided the further evidences for successful formation of BBL-g-PCL copolymer. The thermal properties of BBL-g-PCL copolymers were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). These results indicated that BBL-g-PCL copolymer had relatively good thermal stability. The static contact angle of BBL-g-PCL coating film reached to 80°. The surface functional groups and chemical composition of BBL-g-PCL copolymer was investigated in detail by X-ray photoelectron spectroscopy (XPS). The surface morphology of BBL-g-PCL copolymer was studied by Atomic force microscopy (AFM). Additionally, BBL-g-PCL coating film exhibited high absorption in the ultraviolet (UV) range, which could allow for applications in UV-blocking coatings, as well as the extents for the utilization of lignocellulosic butanol residue.

Combination of lignin and l-lactide towards grafted copolymers from lignocellulosic butanol residue

A series of BBL-graft-poly (L-lactide) copolymers were synthesized via ring-opening polymerization (ROP) of L-lactide (L-LA) with a biobutanol lignin (BBL) initiator and a triazabicyclodecene (TBD) catalyst under free-solvent at 135 °C. By manipulating the mass ratio of BBL/LLA, BBL-g-PLLA copolymers with tunable number-average molecular weight (Mn) (2544-7033 g mol(-1)) were obtained. The chemical structure of PLLA chains was identifiable by FT-IR, (1)H NMR and (13)C NMR spectroscopies, in combination with UV-vis spectra to provide support for the existence of the BBL in the copolymer. This provided solid evidence for the successful synthesis of BBL-g-PLLA copolymer. The thermal properties and surface characterization of BBL-g-PLLA copolymers were different from those of linear PLLA. Furthermore, the BBL-g-PLLA copolymer film showed good absorption capacity in the UV region and high transparency in the visible light region, which was expected to find significant applications in UV-protective coating film.

Facile preparation and characterization of lanthanum-loaded carboxylated multi-walled carbon nanotubes and their application for the adsorption of phosphate ions

A new carboxylated multi-walled carbon nanotubes adsorbent modified with lanthanum hydroxide (MWCNTs-COOH-La) was prepared, characterized and investigated for phosphate removal in batch experiments. The maximum adsorption capacity of the MWCNTs-COOH-La was 48.02xa0mgxa0Pxa0g−1 according to Langmuir model. Structural characterizations demonstrated that the MWCNTs-COOH-La was successfully synthesized and La species was present in the form of La(OH)3. Batch experiments were performed under various conditions (e.g., initial concentrations, temperature, pH, co-existing ions) to investigate the removal of phosphate by MWCNTs-COOH-La. Equilibrium data agreed very well with the Langmuir model, suggesting that the adsorption feature was monolayer. The adsorption behaviors of phosphate were described better by the pseudo-second-order, indicating that the adsorption behaviors were mainly ascribed to chemic-sorption. Phosphate adsorption varied slightly at pH 3–7, but decreased significantly at higher pH values. Phosphate adsorption was slightly influenced by solution ionic strength. A high selectivity of phosphate was also observed in the presence of co-existing anions (except CO32−). The underlying mechanism for the specific adsorption of phosphate by MWCNTs-COOH-La was fully analyzed by X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy technologies. The above results revealed that the hydroxyl groups were involved in the sorption of phosphate and LaPO4 was formed during the adsorption process. This study implied that MWCNTs-COOH-La might be an alternatively viable and promising adsorbent for removal of phosphate from aqueous solution.

Effect of Acid Curing Agent on the Foaming of Liquefied Bamboo-Based Resol Resin

In this paper, effect of acid curing agent on the foaming of liquefied bamboo-based resol resin (PBF) were studied. The research result indicated that the optimal acid curing agent were mixture of p-toluenesulfonic acid and H3PO4, curing of PBF resol resin was analysized in detail and computer-aided software was applied for calculating thermodynamics characteristic of foaming process so that integrative assistantwas controlled better. Its apparent activation energy was 1.226 kJ·mol-1. The PBF foam showed satisfactory densities and compressive properties.