Cellulose-based Graft Copolymers Research Articles

Synthesis and catalytic performance of wood cellulose nanofibers grafted with polylactic acid in rare-earth complexes based on tetrazole carboxylic acids

Stannous octanoate [Sn(Oct)2] and 4-dimethylamino pyridine (DMAP) were used to catalyze the synthesis of amphiphilic cellulose-based graft copolymers, but the acute toxicity of tin ions and DMAP prompts the need for the application of less harmful catalysts. Herein, green catalyst complexes 1–3 [M(H0.5L)2(H2O)5]·2(H2O) (M = Sm, 1; M = Nd, 2; M = Eu, 3; H2L = 4-(3-(tetrazol-5-yl)pyridin-5-yl)benzoic acid) were synthesized, and their properties were systematically investigated. Single-crystal X-ray diffraction showed that the complexes possessed a zero-dimensional structure, while the thermogravimetry and scanning electron microscopy results confirmed their stability after heating at 110 °C for 10 h. Using complexes 1–3 and DMAP as the catalysts, CNFs were grafted with l-lactide via homogeneous ring-opening polymerization to form wood cellulose nanofibers grafted with l-lactide (WGLAs), and the effects of the ratio of wood cellulose nanofibers (WCNFs) to l-lactide ([AGU]/[LA]) and catalyst dosage were studied. The polymerization followed the coordination–insertion mechanism. Under comparable reaction conditions, the grafting ratio of WGLA-1 reached 84.7 %, and the grafting ratio of complex 1 was found to be higher than those achieved using DMAP. WGLAs demonstrated good thermal stability without cytotoxicity, and the residual catalysts in the WGLAs exhibited fluorescence characteristics. Overall, amphiphilic cellulose-based materials with fluorescence emission offered a promising modification strategy to prepare high-performance polymer composites for agriculture and biomedical application.

Synthesis and Characterization of Functional Cellulose–Ether-Based PCL- and PLA-Grafts-Copolymers

The use of biodegradable materials such as cellulose and polyesters can be extended through the combination, as well as modification, of these biopolymers. By controlling the molecular structure and composition of copolymers of these components, it should also be possible to tailor their material properties. We hereby report on the synthesis and characterization of cellulose-based graft copolymers with a precise molecular composition and copolymer architecture. To prepare such materials, we initially modified cellulose through the regioselective protection of the 6-OH group using trityl chloride. The 6-O protected compound was then alkylated, and deprotection at the 6-OH group provided the desired 2,3-di-O-alkyl cellulose compounds that were used as macroinitiators for ring opening polymerization. Regioselective modification was hereby necessary to obtain compounds with an exact molecular composition. Ring opening polymerization, catalyzed by Sn(Oct)2, at the primary 6-OH group of the cellulose macroinitiator, using L-lactide or ε-caprolactone, resulted in graft copolymers with the desired functionalization pattern. The materials were characterized using Fourier-transform infrared spectroscopy, 1H- and 13C- nuclear magnetic resonance spectroscopy, size exclusion chromatography as well as X-ray diffraction, and differential scanning calorimetry. PCL-based copolymers exhibited distinct melting point as well as a crystalline phase of up to 47%, while copolymers with PLA segments were highly amorphous, showing a broad amorphous reflex in the XRD spectra, and no melting or crystallization points were discernible using differential scanning calorimetry.

Synthesis and characterization of cellulose-based graft copolymers crosslinked by gamma-irradiation for enhanced oil recovery applications

Cellulose-based polymers have garnered significant attention as potential candidates for use in enhanced oil recovery (EOR). The challenge in the design of EOR polymers is the need for materials with a high low critical solution temperature (LCST) and the ability to withstand harsh environmental conditions. In this study, cellulose-methylcellulose graft copolymers were prepared with different cellulose to methylcellulose weight ratios. The copolymerization was carried out using gamma radiation doses of 5, 15, and 25 kGy, respectively. The LCST of the copolymers were evaluated using differential scanning calorimetry analysis. The effect of salt addition on the LCST of the materials was studied using different phosphate-buffered saline (PBS) concentrations. The results showed that the cellulose monomer concentration increase from 0.1 to 0.5% in 2% methylcellulose dispersed in water reduced the LCST from 59 to 54°C. The hydrophobic nature of cellulose moieties induced the aggregation of the copolymers into core-shell micelles. Besides, higher gamma radiation doses lowered the LCST of the copolymers. The increase in the salt concentration in the PBS medium tended to decrease the LCST due to disrupted hydration structure of the polymer chains. This work revealed that cellulose-methylcellulose copolymers could be used in chemical EOR due to their high phase transition temperatures, preventing pore clogging and enhancing oil production in the producing wells.

A Study in Sorption of Cu+2 , Fe+2 and I2 onto Graft copolymers of Cellulose with N-Vinyl Pyrrolidone and Butyl Acrylate, and Their Functionalized Derivatives

Cellulose is of special interest due to its abundance in nature and it provides excellent materials for membranes both in native and derivatized forms. Graft copolymers of cellulose when used in separation and enrichment technologies have advantages over the conventional ones, due to chemical resistance, radiation stability and low cost of preparation. Cellulose based graft copolymers and hydrogels offer large hydrophilic area despite being insoluble in water and enrich or separate metal ion by binding, adsorption, chelation and ion exchange processes. Potential of cellulose as sorbent can be improved by radiation and chemical grafting, crosslinking and polymer analogous reactions on some graft copolymers. Grafting of suitable monomers with hydrophobic and hydrophilic/ionic moieties combine high degree of selectivity, permeability and longer stability, and enables complexation with low molecular weight species. Incorporation of functional groups like nitrile, hydrazino, hydroxamic acid and phosphate by derivatization and post polymer reactions enhances metal ion sorption capacity of Cellulosics. In present study an attempt has been made to study the sorption of Fe+2, Cu+2 and I2 on select graft copolymers of cellulose with N-Vinylpyrrolidone (1-Vinyl-2-prrolidone, N-VP) and Butyl Acrylate(BuAc) on to cellulose and some of their functionalized derivatives, on the basis of lowest to highest percent grafting (Pg). An attempt has also been made to investigate selectivity in metal ion sorption and effects of structural aspects of functionalized graft copolymers to find their end-uses as cost effective and eco-friendly polymeric materials for waste water management technologies.

Effects of graft architecture on cellulose-based ordered porous film prepared by breath figures

It is well known that molecular structure has great influence on the porous structure prepared by breath figures. However, the effect of graft architecture on porous structure from graft copolymer is unclear. Here, the cellulose-based graft copolymers with different graft architectures were synthesized and the highly ordered porous films were facilely prepared by breath figure method. The effects of graft architecture with four different structural parameters on porous structure were systematically investigated. It was found that the pore size increased with the increasing graft chain length, main chain length or molecular weight, while the pore size decreased with the increasing graft density under other similar structural parameters. The shorter main chain and the higher graft density resulted in the smaller pore size. Moreover, the shorter main chain was more beneficial for the formation of highly ordered porous structure than the longer main chain. These results will help to understand the effect of graft architecture on porous structure and regulate pore size by adjusting the graft architecture.

Cellulose graft copolymers toward strong thermoplastic elastomers via RAFT polymerization

A novel cellulose-based macromolecular chain transfer agent (Cell-CTA) was designed to prepare cellulose graft copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization. A series of cellulose-graft-poly(n-butyl acrylate-co-acrylamide) (Cell-g-P(BA-co-AM)) copolymers were synthesized as thermoplastic elastomers (TPEs). In this molecular structure, cellulose chains were used as semirigid backbones, whereas the P(BA-co-AM) side chains acted as the rubbery matrix. The glass transition temperatures (Tgs) of Cell-g-P(BA-co-AM) copolymers can be manipulated by tuning the molar ratios between BA and AM during the polymerization process. These cellulose graft copolymers show typical elastomeric behavior and can possess strong tensile strength and high toughness according to the mechanical tests. The random distributed amide groups in AM units can form strong self-complementary hydrogen bonding as supramolecular cross-linking points in the graft copolymers. Morphological results demonstrate the homogeneous state of these Cell-g-P(BA-co-AM) copolymers. This convenient and robust grafting strategy can be further utilized to generate various cellulose-based graft copolymers as sustainable materials via rational molecular design.

Grafted cellulose: a bio-based polymer for durable applications

Grafting is one of the best method for the modification of physicochemical properties of the cellulose. The –OH groups present at C2, C3, and C6 atoms of each β-d-glucopyranose units of cellulose chains are the most susceptible active sites for the grafting of many monomer units or polymers for the formation of a variety of cellulose-based graft copolymers with advanced properties and potential applications as compared to the bare cellulose. In this review article, a brief introduction to get an insight into the structural features of cellulose is given. After that, the potential applications and recent advancements of various cellulose graft copolymers made in fields of controlled drug delivery, adsorption of harmful, toxic and non-biodegradable dyes from industrial effluents, sorption of heavy metal ions from aqueous medium, modification of electrolyte, electrodes and separators of the modern age Lithium ion batteries, and fabrication of smart and innovative food packaging materials are reviewed.

Cellulose-based graft copolymers prepared by simplified electrochemically mediated ATRP

Cellulose-based graft copolymers prepared by simplified electrochemically mediated ATRP

Synthesis, characterization, and micellar behaviors of hydroxyethyl cellulose-graft-poly(lactide/ε-caprolactone/p-dioxanone)

In response to the shortage of petroleum resources and the growing need for sustainable development, cellulose-based amphiphilic copolymers have emerged as a new generation of value-added functional nanostructures from biomass resources. In this article, 17 amphiphilic hydroxyethyl cellulose-based graft copolymers with different side chains, including poly(lactide), poly(e-caprolactone) and poly(p-dioxanone), were synthesized via homogeneous ring opening polymerization in ionic liquid 1-butyl-3-methylimidazolium chloride and characterized by FT-IR, 1H NMR, thermogravimetric analysis and gel permeation chromatography. The resultant copolymers can self-assemble into micelles with a low critical micelle concentration that varies in the range of 0.03–0.24 mg/ml. TEM observations revealed the obtained micelles had a spherical and well-distributed morphology, and DLS analysis showed the nanoscaled sizes were between 40 and 150 nm. These HEC-based micelles can be used as nano-sized vesicles and have great latent forces in drug delivery systems.

Self-Assembly and Paclitaxel Loading Capacity of Cellulose-graft-poly(lactide) Nanomicelles

A series of amiphiphilic cellulose-based graft copolymers (MCC-g-PLA) with various molecular factors were synthesized in ionic liquid BmimCl and characterized by FT-IR, (1)H NMR, (13)C NMR, XRD, and TGA. Their solubility in a variety of solvents was compared. The prepared MCC-g-PLA copolymers can self-assemble into spherical nanomicelles (10-50 nm) in aqueous solution. The self-assembly behaviors of the MCC-g-PLA copolymers were systematically investigated by fluorescence probe. Furthermore, the hydrophobic antitumor drug paclitaxel (PTX) was successfully encapsulated into the MCC-g-PLA micelles. The drug encapsulation efficiency and loading content were found to be as high as 89.30% (w/w) and 4.97%, respectively. Results in this study not only suggest a promising cellulose-based antitumor drug carrier but also provide information for property-directed synthesis of the cellulose graft PLA copolymers.

Cellulose‐based graft copolymers with controlled architecture prepared in a homogeneous phase

AbstractCellulose‐based macroinitiators with predetermined number of initiation sites were synthesized by acylation of microcrystalline cellulose AVICEL PH‐101 with 2‐bromoisobutyryl bromide under homogeneous reaction conditions in the N,N‐dimethylacetamide/LiCl solvent system. The influence of different methods of cellulose activation on acylation efficiency and reproducibility was investigated. Best results were obtained using thermal activation under reduced pressure or the newly introduced protocol based on solvent exchange to 1,4‐dioxane. Prepared macroinitiators were used for grafting with styrene and methyl methacrylate (MMA) using optimized atom transfer radical polymerization reaction conditions to achieve well‐controlled polymerizations with high initiation efficiency. For MMA grafting, the initiation efficiency was shown to be dependent on certain reaction conditions, such as type of solvent, monomer concentration, or the presence of a sacrificial initiator. In addition, single‐electron transfer living radical polymerization with Cu(0) as the catalyst was used for the first time to prepare cellulose‐graft‐polystyrene and cellulose‐graft‐poly(MMA) copolymers in a homogeneous phase. In summary, homogeneous reaction conditions, stoichiometric control in the preparation of macroinitiators, and controlled grafting jointly allowed for an extensive control of copolymers architecture, that is, density of grafting, composition, and molecular parameters of grafts. Moreover, some of the prepared copolymers were characterized by static and dynamic light scattering and microscopic techniques (transmission electron microscopy and atomic force microscopy). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Self-organized ordered microporous thin films from grafting copolymers

Highly ordered porous films of cellulose-based graft copolymers were prepared by the breath figure method upon solvent evaporation. The morphology of the microporous films was investigated by scanning electron microscopy (SEM) and atom force microscopy (AFM). The influences of the preparing conditions, the length and the type of the side chains of copolymers on the morphology of the porous films were investigated. It was found that the average pore size is decreased with increasing the concentration of copolymer solutions and with increasing the side chain length. Moreover, it was confirmed that both the present aggregation in solution and the timely precipitation of copolymer are beneficial for the formation of the ordered microstructure by comparison of solvent and the property of side chains of copolymers. The porous films can be used as the template for the preparation of the micropatterning of fluorescence materials and have the potential applications in many fields such as templates, devices, nanocontainer, photonic and bandgap materials.

Synthesis and Characterization of Novel Temperature and pH Responsive Hydroxylpropyl Cellulose-based Graft Copolymers

In this study, double-hydrophilic hydroxylpropyl cellulose (HPC) based copolymers with poly(Nisopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAA) as graft chains were synthesized and characterized. The release behavior of drug-loaded micelles was studied. The results show that the hydrophilicity of copolymers improves as the pH increases, whereas the hydrophobicity of copolymers enhances as the temperature increases, and all the phase behaviors are reversible. The diameter of micelles decreases and then increases with pH increase. Itshows different micellizing behavior under acidic and basic conditions according to the temperature increase. In vitro release experiments, which used theophylline as a model drug, show that the micelles enhance pH sensitivity in the release process.

Application of a new family of amphoteric cellulose-based graft copolymers as drilling-mud additives

A new family of amphoteric cellulose-based graft copolymers (CGADs), which were prepared by grafting acrylamide and dimethylaminoethyl methacrylate onto sodium carboxymethyl cellulose, have been investigated for their properties as multifunctional drilling-mud additives with respect to shale inhibition, rheological control and filtrate-loss control. For the CGADs investigated, the shale-inhibition ability improves but the filtration-control ability weakens with increasing content of cationic groups. An increase in the concentration of CGADs results in better inhibition and viscosity-building as well as lower fluid loss. The pH of the medium has an effect on the inhibitive property. A comparative study among CGADs and some commercial polymeric drilling-mud additives was also carried out.