Optical and Mechanical Properties of CMCNF-dispersed MMT/CMC-Na Nanocomposite Films: Influence of the Degree of Substitution of CMCNFs

Carboxymethylated cellulose nanofibril(CMCNF)is an effective green dispersant to prepare well-dispersed monolayer montmorillonites(MMTs)in water,thereby facilitating the preparation of a high-performance MMT/polymer nanocomposite film.However,not enough attention has been paid to correlating the degree of substitution(DS)of CMCNFs with the mechanical and optical properties of the final nanocomposite films.In this study,a series of homogeneous monolayer MMT nanoplatelet dispersions was prepared initially using CMCNFs with different DS as a dispersant,and the as-prepared CMCNF-dispersed MMT dispersions were then mixed with sodium carboxymethyl cellulose(CMC-Na)to fabricate nacre-like nanocomposite films with different contents of MMTs through self-assembly.The layered nanostructure and optical and mechanical properties of the asprepared CMCNF-dispersed MMT/CMC-Na nanocomposite films were investigated,which demonstrated that CMCNFs with lower DS have a positive effect on their optical and mechanical properties.This study sheds light on the preparation of MMT-based nanocomposite films with superior optical and mechanical properties.

Preparation and Characterization of Acylated Chitosan

Fully acylated chitosan and N, N-diacyl chitosan were prepared. The products were characterized by elemental analysis, FTIR and 1H NMR. The experimental results indicate that the average degree of acylation depends on the volume ratio of pyridine to chloroform in the reaction medium, the chain length of the acylation agent used, and the molecular weight of chitosan raw materials. The XRD measurements were carried out for pure chitosan, fully acylated chitosan and N, N-diacyl chitosan to verify the crystallinity change caused by the acylation.

STUDY ON THE CHARACTERIZATION OF DISTRIBUTION OF SUBSTITUENTS ALONG THE CHAINOF CARBOXYMETHYL CELLULOSE

Four new paranmeters, and , and have been proposed to describe the average length of the sequence of substituted anhydroglucose units and that of unsubstituted ones respectively along the CMC chain. The methods for determining those parameters have also been presented . Six CMC samples have been characterized in terms of intrinsic viscosity, degree of substitution （DS）, index of substitution（SI）;and . It has been proved experimentally that, not only can describe the sequence distribution along the CMC chain, but also can be used for calculating SI and estimating the average degree of substitution in the substituted glucose rings.

Chiral Separation Abilities of Homogeneously Synthesized Cellulose 3,5-Dimethylphenylcarbamates: Influences of Degree of Substitution and Molecular Weight

A series of cellulose 3,5-dimethylphenylcarbamates （CDMPCs） with different degrees of substitution （DS） and degrees of polymerization （DP） were homogeneously synthesized in 1-allyl-3-methylimidazolium chloride （AmimC1）. Then, the CDMPCs were coated on silica gel and used as chiral stationary phases （CSPs）, and their chiral recognition abilities for seven racemates were evaluated by high performance liquid chromatography. The results showed that DS and DP of CDMPCs had a great influence on chiral recognition abilities of the CSPs. The CSPs with the DS ~ 1 gives a low chiral recognition to most racemates. On the contrast, the CSPs with the DS _〉 2 exhibited high chiral separation abilities. For example, six racemates could be separated on the CSP with CDMPC of DS ~ 2 （CSP-2）. Especially, for the enantioseparation of 1-（2-naphthyl） ethanol and Tr6ger＇s base, CSP-2 gave the highest separation ability in all of CSPs. On the other hand, when the DP of cellulose was in a range from 39 to 220, the chiral separation abilities of CDMPCs increased as the DP increased. This work demonstrates that the structure of cellulose esters such as DS and DP has important effect on their chiral separation ability, and therefore provides a practical method to design and prepare desirable CSPs for different racemates.

Effects of degree of substitution on stearic acid-modified Bletilla striata polysaccharides nanoparticles and interactions between nanoparticles and bovine serum albumin

Three kinds of stearic acid（SA）-modified Bletilla striata polysaccharides（BSPs-SA） conjugates with different degrees of substitution（DS） values of SA moiety were synthesized. The impacts of the DS values on the properties of BSPs-SA self-aggregated nanoparticles were determined. The interactions between bovine serum albumin（BSA） and the BSPs-SA nanoparticles were characterized using spectroscopic observations. The cytotoxicity was measured through 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyl tetrazolium bromide（MTT） method. The critical aggregation concentration and the average particle sizes reduced from 16.81 μg/mL to 3,09 μg/mL and 192.70 nm to 125.29 nm when the DS values of SA segment increased from 4.98% to 12.94%, respectively. The cumulative release percentage of docetaxel in BSPs-SA nanoparticles decreased whereas encapsulation efficiency and loading capacity increased along with the DS increase of SA moiety. The fluorescence and ultraviolet results demonstrated that the conformation of BSA did not show significant change after incubating with BSPs-SA nanoparticles.Besides, the mass ratio of BSA/BSPs-SA affected their affinity intensity. The inhibition capability of cell proliferation of docetaxel-loaded BSPs-SA nanoparticles against 4 T1 was superior to that of Duopafei;.BSPs-SA nanoparticles may become a promising nanocarrier for anticancer drugs by adjusting the DS values of the hydrophobic SA groups.

Sustainable conversion regenerated cellulose into cellulose oleate by sonochemistry

Derivatization has great potential for the high-value utilization of cellulose by enhancing its processability and functionality.However,due to the low reactivity of natural cellulose,it remains challenging to rapidly prepare cellulose derivatives with high degrees of substitution.The“cavitation effect”of ultrasound can reduce the particle size and crystalline index of cellulose,which provides a possible method for preparing cellulose derivatives.Herein,a feasible method was proposed for efficiently converting regenerated cellulose to cellulose oleate with the assistance of ultrasonic treatment.By adjusting the reaction conditions including ultrasonic intensity,feeding ratios of oleic acid,reaction time,and reaction solvent,a series of cellulose oleates with degrees of substitution ranging from 0.37 to 1.71 were synthesized.Additionally,the effects of different reaction conditions on the chemical structures,crystalline structures,and thermal behaviors were investigated thoroughly.Cellulose oleates with degrees of substitution exceeding 1.23 exhibited amorphous structures and thermoplasticity with glass transition temperatures at 159.8 to 172.6℃.This study presented a sustainable and practicable method for effectively derivatizing cellulose.