Study of Structural Characteristics of Cellulose Esters with Different Degrees of Substitution

In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphatic acids.The specific gravity of the highly substituted samples was measured by a pycnometric method in the aqueous medium.To calculate the molar,Van der Waals,and free volumes,as well as the packing coefficient of amorphous esters the method of additive contributions of partial volumes of atoms and atom groups in the volumes of polymers was used.Based on the molar volume,also specific gravity of cellulose esters was calculated.The coincidence of calculated and experimental characteristics was shown.In addition,the relationship between glass transition temperature and free volume was found for the esters.The theoretical equations were derived,which provide predicting the structural characteristics of cellulose esters with different degrees of substitution.

Effect of Molecular Structure on the Gas Permeability of Cellulose Aliphatate Esters

In this work, four kinds of cellulose aliphatate esters, cellulose acetate （CA）, cellulose propionate （CP）, cellulose butyrate （CB） and cellulose acetate butyrate （CAB） are synthesized by the homogeneous acylation reactions in cellulose/AmimC1 solutions. These cellulose aliphatate esters are used to prepare gas separation membranes and the effects of molecular structure, such as substituent type, degree of substitution （DS） and distribution of substituents, on the gas permeability are studied. For CAs, as the DS increases, their gas permeabilities for all five gases （02, N2, CH4, CO and CO2） increase, and the ideal permselectivity significantly increases first and then slightly decreases. At similar DS value, the homogenously synthesized CA （distribution order of acetate substituent： C6 〉 C3 〉 C2） is superior to the heterogeneously synthesized CA （distribution order of acetate substituent： C3 〉 C2 〉 C6） in gas separation. With the increase of chain length of aliphatate substituents from acetate to propionate, and to butyrate, the gas permeability of cellulose aliphatate esters gradually increases. The cellulose mixed ester CAB with short acetate groups and relatively long butyrate groups exhibits higher gas permeability or better permselectivity than individual CA or CB via the alteration of the DS of two substituents.

A comparative study on environmental surveillance of enterovirus:Using a two-phase separation method and a filtration method with a mixed cellulose ester(MCE)membrane

This study aimed to compare the sensitivity of two-phase separation and the filtration method using a mixed cellulose ester(MCE)membrane to detect enteroviruses in sewage samples.From December 2015 to July 2016,four domestic sewage samples(1 L/sample)were collected monthly from the Guangzhou Liede Sewage Treatment Plant,and each sewage sample was divided into two aliquots(500 mL).The sewage sample was concentrated using the two-phase separation and the filtration method using an MCE membrane,and the treated solutions were inoculated into cells for enterovirus isolation.Polymerase chain reaction amplification,VP1 sequencing,and enterovirus molecular typing were performed on the positive isolates.The detection rates of poliovirus(PV)and non-polio enterovirus(NPEV)obtained using the filtration method using an MCE membrane were higher than those using the two-phase separation method.McNemar's test showed that the detection rates of PV,NPEV,type 1 Sabin-like(SL1),type 2 Sabin-like(SL2),and type 3 Sabin-like(SL3)strain were not statistically significant(P>0.05).In Guangdong Province,China,the detection rates for PV and NPEV were 53.13%and 62.50%(20/32),respectively.Twenty-seven PVs were isolated,three highly variable strains of the type 1 vaccine,with seven nucleotide substitutions in the VP1 region,compared with the type 1 Sabin strains.Eighty-seven strains of NPEV were isolated and nine serotypes were identified,among which coxsackievirus B3(CVB3),echovirus 6(E6),and echovirus 11(E11)were the dominant strains.The filtration method using an MCE membrane is more sensitive than two-phase separation and can be used as a robust,sensitive,and cost-effective method to isolate enteroviruses from sewage.

Electrolyte additive maintains high performance for dendrite-free lithium metal anode

Because of their high capacity and low potential,lithium metal anodes are considered to be promising candidates for next generation electrode materials.However,the safety concerns and limited cycling life associated with uncontrollable dendrite growth hamper practical applications.In this work,the acidified cellulose ester,which is a mixed fiber microporous membrane film,was used as a novel electrolyte additive that effectively improves the cycle stability of the lithium metal anode and inhibits dendrite growth.The focus of this paper is on inhibiting the formation and growth of lithium dendrites.The coulombic efficiency of a Li|Cu battery with this acidified cellulose ester additive remains stable at 99%after 500 cycles under a current density of 1 mA/cm^2.Symmetric batteries also remain stable after 500 cycles(1000 h)under a current density of 1 mA/cm^2.These superior properties can be ascribed to the induced nucleation and the uniform distribution of lithium ion flux.This study uncovers an approach for effectively enabling stable cycling of dendrite-free lithium metal anodes.

Comparison of concentration methods for detection of hepatitis A virus in water samples

Hepatitis A virus is a pathogen associated with water pollution.Contaminated drinking water can cause hepatitis A outbreaks,lead to economic losses,and even threaten human lives.It is difficult to detect low levels of hepatitis A virus in water,so the virus must be concentrated in order to quantify it accurately.Here,we present a simple,rapid,efficient technique for the concentration and detection of hepatitis A virus in water.Our data showed that adding phosphate-buffered saline to the water,pre-filtering the water,and adding Trizol reagent directly to the filtration membrane can significantly improve concentration efficiency.Of three types of filtration membranes studied(mixed cellulose ester membrane,polyvinylidene fluoride membrane,and nylon membrane),the concentration efficiency using mixed cellulose ester membrane with a 0.1-μm pore size was the highest,reaching 92.62 ± 5.17%.This method was used to concentrate hepatitis A virus in water samples from Donghu Lake.Using SYBR Green real-time reverse transcription polymerase chain reaction analysis,the detection sensitivity of this method reached 10~1 copies/μL and its concentration efficiency reached 79.45 ± 9.88%.