The conventional cellulose nitrate (NC), used in many applications such as coating agent, main charge of propellant, museum artefacts, biofilter material, solid-phase immobilization supports for proteins, was mainly prepared from wood or cotton. The conventional NC presents many drawbacks such as low density, high friability and low combustion temperature. One approach to improve these shortcomings is the modification of the structure of the NC precursor (cellulose). In this work, microcrystalline cellulose nitrate was successfully produced from an inexpensive and easily renewable source which is Alfa grass. Fourier transform infrared spectroscopy indicates some modifications in the peak positions and intensities, suggesting that a significant difference between conventional and microcrystalline cellulose nitrate samples exists. According to X-ray diffraction results, microcrystalline cellulose nitrate samples were more crystalline than the conventional cellulose nitrate samples, where the increase of the crystallinity is 22 %. The morphology was investigated using scanning electron microscopy, showing a compact structure and a rough surface. In comparison with the commercial nitrocellulose material, the microcrystalline cellulose nitrate particles have good thermal stability, low viscosity, high nitrogen content and important quantity of gas released. Besides on these results, Alfa microcrystalline cellulose nitrate showed tremendous potential use as a propellant and gas generator component or other high value-added applications.

Physicochemical properties of microcrystalline nitrocellulose from Alfa grass fibres and its thermal stability

Effect of enzymatic hydrolysis on the morphology and fine structure of pretreated cellulosic residues

In alkane solvents, poly(isoprene-b-ferrocenyldimethylsilane) (PI-b-PFS) block copolymer forms fiberlike micelles, which show intriguing similarities with biological fibers such as amyloid fibers. Both systems exhibit fiber growth by a nucleated self-assembly mechanism and rapidly fragment upon exposure to the shear forces of ultrasonic irradiation. Sonication of PI-b-PFS cylindrical micelles was studied quantitatively by static light scattering and by electron microscopy. Both techniques are in excellent agreement and show that the weight-average length of sonicated micelles decreases as a function of sonication time. Simulation of the cleavage of micelles using different scission models shows that micelle fragmentation follows a Gaussian model and that the scission is highly dependent on micelle length, in contrast to DNA and polymer chain scission. We speculate that biological fibers, which are similar in length and rigidity to PFS block copolymer micelles, fragment by a similar mechanism when subjected to sonication.

Fragmentation of fiberlike structures: sonication studies of cylindrical block copolymer micelles and behavioral comparisons to biological fibrils.

https://repositorium.sdum.uminho.pt/bitstream/1822/6159/1/Pala-CarbohydratePol2007.pdf

Enzymatic depolymerisation of cellulose

https://arpi.unipi.it/bitstream/11568/930123/1/Full%20paper2.pdf

Effect of ball-milling on crystallinity index, degree of polymerization and thermal stability of cellulose

Two samples of cellulose (molecular weight 2.97 × 105 and 1.25 × 105) were transformed into carbanilates (CTC) which were then fractionated by the elution method at a constant composition of the acetone-water elution mixture with the column temperature gradually increasing from −30°C to 30°C, and by the GPC method in acetone and tetrahydrofuran. Tetrahydrofuran appeared to be a more suitable solvent. The molecular weights of fractions obtained by the elution fractionation were determined by the light-scattering method in tetrahydrofuran. The width of fractions was determined by the GPC method (average Mw/Mn = 1.37); the [η] values and the Mark-Houwink constants (K = 5.3 × 10-3, a = 0.84) for tetrahydrofuran at 25°C were determined. The calibration curve for the GP method was constructed by means of the fractions thus obtained; it was demonstrated that the universal calibration curve according to Benoit can also be used. It was demonstrated that the molecular weight distribution of cellulose can be conveniently determined by conversion into CTC followed either by the elution fractionation (for preparative purposes) or by fractionation by the GPC method (for analytical purposes).

Determination of molecular weight distribution of cellulose by conversion into tricarbanilate and fractionation

Polymerization Of Conjugated Dienes To Ladder Cyclopolymers And The Cyclization Of Stereoregular Diene Polymers

The molecular weight distribution functions of polystyrene degraded by shear stress in isopropylphenyl phosphate solution were compared with the calculated ones, obtained by assuming that up to a certain distance from each chain end the probability of bond scission is zero. Two phenomenological models were proposed for the probability of degradation in the central part of the chain. A comparison with experimental data suggests that the probability of degradation increases towards the center of the chain. Branched fractions formed by degradation in the presence of air were found to be present by the GPC method with on-line viscometric detection.

Degradation of polystyrene by shear stress in isopropylphenyl phosphate solution

The γ-ray-initiated polymerization of butadiene, isoprene, and 2,3-dimethylbutadiene-1,3 was carried out at temperatures of 20°C. and −78°C. Polymers of butadiene and isoprene with mixed linear and cyclic structure were proved to result from the polymerization at −78°C. A monocyclic structure was found for the 2,3-dimethylbutadiene-1,3 polymers initiated either at −78°C. or in the thiourea canal complex at 20°C.

Cyclo‐ and cyclized diene polymers. XIII. γ‐Ray‐initiated polymerization of 1,3‐dienes

The Mark-Houwink constants K = 25 x 10−2, a = 0625 were determined for the system poly(methyl methacrylate) — dimethylformamide at 25°C using narrow fractions (Mw/Mn from 100 to 155) in the molecular weight range from 119×105 to 194×105 as determined by the light scattering method and osmometrically

I. Kössler

Papers

Determination of molecular weight distribution of cellulose by conversion into tricarbanilate and fractionation

Polymerization Of Conjugated Dienes To Ladder Cyclopolymers And The Cyclization Of Stereoregular Diene Polymers

Degradation of polystyrene by shear stress in isopropylphenyl phosphate solution

Cyclo‐ and cyclized diene polymers. XIII. γ‐Ray‐initiated polymerization of 1,3‐dienes

The Mark-Houwink constants for poly(methyl methacrylate) in N,N-dimethylformamide