A Comparative Simulation:Difference between Chemical Grafting and Physical Doping of Cellulose by Using Polysilsesquioxane

In order to study the effect of different modification methods on polysilsesquioxane(POSS)modified cellulose,a molecular dynamics method was used to establish a pure cellulose model and a series of modified models modified by polysilsesquioxane in different ways.And their thermodynamic properties were calculated.The results showed that the performance of cellulose models was better than that of unmodified model,and the modified effect was the best when two cellulose chains were grafted onto polysilsesquioxane by chemical bond(M2 model).Compared with pure cellulose model,the cohesive energy density and solubility parameters of M2 model are increased by 9%,and the values of tensile modulus,bulk modulus,shear modulus and Cauchy pressure increased by 38.6%,29.5%,41.1% and 29.5%,respectively.In addition,the free volume fraction and mean square displacement of each model were calculated and analyzed in this work.Compared with the pure cellulose model,the molecular chain entanglement of cellulose was increased due to the existence of the chemical bonds in the M2 model,which made the cellulose molecular chains occupy more free volume,so that the system had a smaller free volume fraction,inhibited the chain movement of cellulose chains,and thus improved the thermal stability of cellulose.

Improving the physical properties of nano-cellulose through chemical grafting for potential use in enhancing oil recovery

The performance of nano-cellulose fluid as a"green"flooding agent in enhancing oil recovery was evaluated in our previous study.Expanding upon our prior findings,in this study the physical properties of nano-cellulose were further improved through chemical grafting with 2-acrylamido-2-methylpropane sulfonic acid monomer(AMPS)and alkyl chain.Scanning electron microscopy(SEM)observation indicated that the morphology of the nano-cellulose maintained fibrillar and was not altered after the chemical modification.The thermal stability of the AMPS and alkyl chain grafted nano-cellulose was investigated through thermogravimetric analysis(TGA).A similar thermal response behavior was observed for the three evaluated samples.Compared to the non-grafted nano-cellulose,the grafted nano-cellulose remained homogenous in an electrolyte solution against storage time,suggesting a superior sanity-tolerance.Rheological analysis also proved the advanced viscoelastic properties of the nano-cellulose dispersion.

Acellular allogeneic nerve grafting combined with bone marrow mesenchymal stem cell transplantation for the repair of long-segment sciatic nerve defects:biomechanics and validation of mathematical models

We hypothesized that a chemically extracted acellular allogeneic nerve graft used in combination with bone marrow mesenchymal stem cell transplantation would be an effective treatment for long-segment sciatic nerve defects.To test this,we established rabbit models of 30 mm sciatic nerve defects,and treated them using either an autograft or a chemically decellularized allogeneic nerve graft with or without simultaneous transplantation of bone marrow mesenchymal stem cells.We compared the tensile properties,electrophysiological function and morphology of the damaged nerve in each group.Sciatic nerves repaired by the allogeneic nerve graft combined with stem cell transplantation showed better recovery than those repaired by the acellular allogeneic nerve graft alone,and produced similar results to those observed with the autograft.These findings confirm that a chemically extracted acellular allogeneic nerve graft combined with transplantation of bone marrow mesenchymal stem cells is an effective method of repairing long-segment sciatic nerve defects.

Surface modification of polyolefin separators for lithium ion batteries to reduce thermal shrinkage without thickness increase

Surface chemical modification of polyolefin separators for lithium ion batteries is attempted to reduce the thermal shrinkage, which is im- portant for the battery energy density. In this study, we grafted organic/inorganic hybrid crosslinked networks on the separators, simply by grafting polymerization and condensation reaction. The considerable silicon-oxygen crosslinked heat-resistance networks are responsible for the reduced thermal shrinkage. The strong chemical bonds between networks and separators promise enough mechanical support even at high temperature. The shrinkage at 150 ℃ for 30 min in the mechanical direction was 38.6% and 4.6% for the pristine and present graft-modified separators, respectively. Meanwhile, the grafting organic-inorganic hybrid crosslink networks mainly occupied part of void in the internal pores of the separators, so the thicknesses of the graft-modified separators were similar with the pristine one. The half cells prepared with the modified separators exhibited almost identical electrochemical properties to those with the commercial separators, thus proving that, in order to enhance the thermal stability of lithium ion battery, this kind of grafting-modified separators may be a better alternative to conventional silica nanoparticle layers-coated polyolefin separators.

A Review of Hydrophobic Nanocellulose and Its Applications

Nanocellulose is of great interest in various areas nowadays as a natural nanostructured biomaterial.However,in many applications,the high hydrophilicity due to a large number of hydroxyl groups is not desired.The hydrophobic modification of nanocellulose can thus increase its application.This work reviewed recent developments of methods for nanocellulose hydrophobic modification,through physical adsorption and chemical grafting.The applications of hydrophobic nanocellulose were also reviewed.