Material Functionalization of Cellulose and Related Polysaccharides via Diverse Microcompositions

Environmentally friendly covalent coupling of proteins onto oxidized cellulosic materials

Cellulose is a biodegradable and renewable material that is one of the most abundant biopolymers with many different applications from low value newsprint products to high value biomedical sensor devices.

Utilization of Lignocellulosic Biomass via Novel Sustainable Process

In this review, we show novel methods for utilizing lignocellulosic biomass, polysaccharides, and lignin. Firstly, the simultaneous enzymatic saccharification and comminution (SESC) of plant materials is described as an extraction method for lignocellulosic biomass that does not require toxic reagents or organic solvents. Secondly, we demonstrate the material utilization of non-deteriorated lignocellulosic biomass extracted by SESC, such as for sugar and ethanol synthesis, and as a heatproof filler. Finally, we exhibit the use of a functional monomer (e.g., in disinfection chemicals, cesium chelation, and building blocks for polymers), 2-pyrone-4,6-dicarboxylic acid, derived from lignin via metabolic degradation.

Olefin Cross-Metathesis in Polymer and Polysaccharide Chemistry: A Review

Olefin cross-metathesis, a ruthenium-catalyzed carbon-carbon double bond transformation that features high selectivity, reactivity, and tolerance of various functional groups, has been extensively applied in organic synthesis and polymer chemistry. Herein, we review strategies for performing selective cross-metathesis and its applications in polymer and polysaccharide chemistry, including constructing complex polymer architectures, attaching pendant groups to polymer backbones and surfaces, and modifying polysaccharide derivatives.

Functional thermoplastic materials from derivatives of cellulose and related structural polysaccharides

This review surveys advances in the development of various material functionalities based on thermoplastic cellulose and related structural polysaccharide derivatives. First, the dependence of thermal (phase) transition behavior on the molecular composition of simple derivatives is rationalized. Next, approaches enabling effective thermoplasticization and further incorporation of material functionalities into structural polysaccharides are discussed. These approaches include: (a) single-substituent derivatization, (b) derivatization with multi-substituents, (c) blending of simple derivatives with synthetic polymers, and (d) graft copolymerization. Some examples addressing the control of supramolecular structures and the regulation of molecular and segmental orientations for functional materials fabrication, which have especially progressed over the past decade, are also addressed. Attractive material functions include improved mechanical performance, controlled biodegradability, cytocompatiblity, and optical functions.

Study of Reactive Melt Processing Behavior of Externally Plasticized Cellulose Acetate in Presence of Isocyanate

Two types of externally plasticized cellulose acetate (CA) were chemically modified using 4,4'-methylene diphenyl diisocyanate (MDI) as crosslinking agent. Crosslinking was performed in the molten state by means of melt mixing in an internal mixer. The viscoelastic properties of the non-crosslinked, externally plasticized CA show typical temperature dependence, similar to conventional thermoplastics. A strong increase in storage modulus is observed with increasing crosslink density indicating that the crosslinked compounds exhibit predominately elastic response. The complex viscosity also increases considerably with increasing crosslink density and does not reach the typical Newtonian plateau at low radial frequencies any more. The viscoelastic properties correlate well with the data recorded online during reactive melt processing in the internal mixer. In comparison to the non-crosslinked CA, the crosslinked compounds show higher glass transition temperature, higher VICAT softening temperatures, improved thermal stability and lower plasticizer evaporation at evaluated temperatures.

Blend miscibility of cellulose propionate with poly(N-vinyl pyrrolidone-co-methyl methacrylate)

The blend miscibility of cellulose propionate (CP) with poly(N-vinyl pyrrolidone-co-methyl methacrylate) (P(VP-co-MMA)) was investigated. The degree of substitution (DS) of CP used ranged from 1.6 to >2.9, and samples for the vinyl polymer component were prepared in a full range of VP:MMA compositions. Through DSC analysis and solid-state (13)C NMR and FT-IR measurements, we revealed that CPs of DS<2.7 were miscible with P(VP-co-MMA)s of VP≥~10mol% on a scale within a few nanometers, in virtue of hydrogen-bonding interactions between CP-hydroxyls and VP-carbonyls. When the DS of CP exceeded 2.7, the miscibility was restricted to the polymer pairs using P(VP-co-MMA)s of VP=ca. 10-40 mol%; the scale of mixing in the blends concerned was somewhat larger (ca. 5-20 nm), however. The appearance of such a "miscibility window" was interpretable as an effect of intramolecular repulsion in the copolymer component. Results of DMA and birefringence measurements indicated that the miscible blending of CP with the vinyl polymer invited synergistic improvements in thermomechanical and optical properties of the respective constituent polymers. Additionally, it was found that the VP:MMA composition range corresponding to the miscibility window was expanded by modification of the CP component into cellulose acetate propionate.

Mechanical and viscoelastic properties of cellulose nanocrystals reinforced poly(ethylene glycol) nanocomposite hydrogels

The preparation and mechanical properties of elastomeric nanocomposite hydrogels consisting of cellulose nanocrystals (CNCs) and poly(ethylene glycol) (PEG) are reported. The aqueous nanocomposite CNC/PEG precursor solutions covalently cross-linked through a one-stage photocross-linking process. The mechanical properties of nanocomposite hydrogels, including Young's modulus (E), fracture stress (σ), and fracture strain (ε), were measured as a function of CNC volume fraction (φCNC, 0.2-1.8%, v/v) within polymeric matrix. It was found that the homogeneously dispersed nanocomposite hydrogels can be prepared with φCNC being less than 1.5%, whereas the heterogeneous nanocomposite hydrogels were obtained with φCNC being higher than 1.5%. The nanocomposite hydrogels exhibited higher strengths and flexibilities when compared with neat PEG hydrogels, where the modulus, fracture stress, and fracture strain enhanced by a factor of 3.48, 5, and 3.28, respectively, over the matrix material alone at 1.2% v/v CNC loading. Oscillatory shear data indicated the CNC-PEG nanocomposite hydrogels were more viscous than the neat PEG hydrogels and were efficient at energy dissipation due to the reversible interactions between CNC and PEG polymer chains. It was proposed that the strong gel viscoelastic behavior and the mechanical reinforcement were related to "filler network", where the temporary interactions between CNC and PEG interfered with the covalent cross-links of PEG.

Ester prodrug-loaded electrospun cellulose acetate fiber mats as transdermal drug delivery systems

Cellulose acetate (CA) fibers loaded with the ester prodrugs of naproxen, including methyl ester, ethyl ester and isopropyl ester, were prepared through electrospinning using acetone/N,N-dimethylacetamide(DMAc)/ethanol (4:1:1, v/v/v) as solvent. The chemical and morphological characterizations of the medicated fibers were investigated by means of SEM, DSC, XRD and FTIR, as well as the studies of the drug release properties. The results indicated that the morphology and diameter of the fibers were influenced by the concentration of spinning solution, applied voltage, electrospun solvent and the surfactants. The average diameters of the fibers ranged between 100 and 500 nm for three prodrugs. There was good compatibility between CA and three prodrugs in the blended fibers, respectively. In vitro release indicated that constant drug release from the fiber was observed over 6 days. The prodrugs were successfully encapsulated into the fibers, and this system was stable in terms of effectiveness in release.