Grafting Branch Length and Density Dependent Performance of Zwitterionic Polymer Decorated Polypropylene Membrane

Branch length and density have critical effects on membrane performances; however, it is regarded to be traditionally difficult to investigate the relationship due to the uncontrolled membrane modification methods. In this study, zwitterionic polymer with controlled grafting branch chain length（degree of polymerization） and grafting density（grafting chains per membrane area） was tethered to the microporous polypropylene membrane surface based on the combination of reversible addition-fragmentation chain transfer（RAFT） polymerization technique with click reaction. The modified membranes were tested by filtrating protein dispersion to highlight the correlations of branch chain length and grafting density with the membrane permeation performances. The pure water flux, the flux recovery ratio are positively and significantly, and the irreversible fouling negatively and significantly correlated with grafting density. These results demonstrate that the larger the coverage of the membrane with poly{[2-（methacryloyloxy）ethyl]-dimethyl-（3-sulfopropyl） ammonium hydroxide}（PMEDSAH）, the higher the pure water flux and the higher the flux recover ratio, and the lower the irreversible fouling, which shows that high grafting density is favorable to fouling reducing.

Preparation and Performance of Collagen Modified Polyester Used as Implantable Artificial Hair

The implantable artificial hair was prepared by grafting collagen on the surface of poly( ethylene terephthalate)( PET) to improve its biocompatibility. Acrylic acid( AAc) was used to modify the surface properties of PET firstly,and then collagen was grafted on the PET-AAc surface. The concentration of collagen solution was discussed to graft more collagen on PET surface. Composites were well characterized by scanning electron microscopy( SEM),Fourier transform infrared spectroscopy( FTIR) and X-ray photoelectron spectroscopy( XPS). SEM indicated that collagen with about 3. 07μm thickness was coated on PET surface when the concentration of collagen solution was 1. 0 mg/m L. FTIR and XPS showed AAc and collagen were both on the surface of PET monofilaments. The optimized concentration of collagen solution was 1. 0 mg/m L,resulting in the most grafting density of 3. 46 μg/cm2. It can be concluded that a large amount of collagen is coated on PET surface.

In situ investigation of lysozyme adsorption into polyelectrolyte brushes by quartz crystal microbalance with dissipation

A well understanding about protein adsorption into charged polymer brushes is of importance in the elucidation of mechanism and important phenomena(such as “chain delivery”effect) in protein adsorption on polymer-grafted ion exchange adsorbents. In this work, quartz crystal microbalance with dissipation(QCM-D) was introduced to in situ investigate lysozyme adsorption on QCM sensors grafted with poly(3-sulfopropyl methacrylate)(pSPM) via atom transfer radical polymerization. It was achieved by analyzing frequency(f) and energy dissipation(D) shift simultaneously on pSPM-grafted sensors. The result showed that an initial decrease in ΔD was typical of lysozyme adsorption on pSPM-grafted sensor and more significant with an increase of chain length and grafting density. It was attributed to significant water release in the hydration layer of protein and polymer chains in lysozyme adsorption into pSPM brushes.On pSPM-grafted sensors with long and dense chains, furthermore, lysozyme transitioned from monolayer to multilayer adsorption and the maximum adsorbed amount was obtained to be 374.0 ng·cmamong all pSPM-grafted sensors in this work. The results in D-f plot further revealed that lysozyme adsorption into pSPM brushes increased the rigidity of adsorbed layer and little structure adjustment of adsorbed lysozyme. It was unfavorable for “chain delivery” effect for facilitated transport of adsorbed protein. This work provided valuable insight into protein adsorption in pSPM brushes and outlined a feasible approach to increasing mass transport in polymer-grafted ion exchange adsorbents.

Surface Modification of Barium Sulfate Particles

In this study, surface modification of barium sulfate was investigated using several model molecules for chemical treatment: ethanesulfonic acid, butyric acid, trimethoxy(propyl) silane and phosphoric acid 2-hydroxyethyl methacrylate. Samples were characterized by FT-IR and TGA to check the capability of these model molecules to interact with BaSO4 surface. The results pointed out the presence of an organic layer around the surface after the chemical treatment even after several washings to remove all species in excess. Model molecules were grafted onto BaSO4 surface and grafted density was determined. It reveals that phosphoric acid and carboxylic acid are the best candidates for the modification of BaSO4 surface. Both can be used as anchoring groups to modify the hydrophilic balance of barium sulfate surface in order to avoid the formation of aggregates and to improve the compatibility of this filler within hydrophobic polymer matrix.

Physical Insight for Grafting Polymer Chains onto the Substrate via Computer Simulations:Kinetics and Property

Molecules adsorbed or attached on a surface is a quite basic phenomenon in numerous chemical or biological systems.Grafting-onto is considered as a feasible way to achieve it.The grafting reaction is essentially controlled by the diffusion of the molecules,thus it is more likely a physical issue,instead of a chemical issue.Because of the experimental difficulty in measuring the properties of surface-attached molecules(e.g.,the polymeric molecules),the surface-bound molecules are often assumed as with the same properties as that of the start feeding ones in solution.This assumption was even used to guide further characterization,while it is proved to be invalid by different quantifying methods.Consequently,an effective prediction for the properties of surface-bound molecules is still lacking.Based on a microscopic level and a dynamic perspective,the grafting process onto a flat substrate with polydisperse feeding polymeric molecules is investigated in-depth by coarse-grained Brownian dynamics simulation as well as model analysis.We find from simulations that for the final grafting densityσ_(g)and the mean chain length of start feeding molecules<N_(0)>,the dependence ofσ_(g)-<N_(0)>^(γ)with the constant exponential factorγmay be a determined rule for one-end functionalized flexible linear polymer chains grafting on the flat substrate.Since grafting-onto is a multiple interplayed process,our simulation study indicates that there is an optimized initial concentration of start feeding molecules for achieving high grafting density of surface-bound polymers.We also propose a correctional equation to quantitatively predict the molecular weight distribution(MWD)of surface-bound polymeric molecules,which may be effective for predicting the MWD of the surface-bound ones in specific conditions.This simulation study helps to better understand the kinetics of grafting-onto process,and serves as a theoretical guide to achieve the precise design of surface modification materials via grafting-onto strategy.

Controllable Synthesis of a Well-defined Polypropylene grafted Silica Nanoparticles and Its Effect on Crystallization Behavior of Polypropylene

Well-defined polypropylene grafted silica nanoparticles(PP-g-SiO_(2))were prepared through the reaction of maleic anhydride grafted polypropylene(PP-g-MAH)with amino-functionalized silica(SiO_(2)-NH_(2))by the'grafting-to'method.The grafting density of PP-g-SiO_(2) is found to be controlled by the concentration of silane coupling agent 3-[2-(2-aminoethylamino)ethyl amino]propyl trimethoxy silane(TAMS).The maximum grafting density of grafted PP-g-MAH chains with molecular weight of 9100 g/mol could reach 0.34 chains/nm~2,when the critical concentration of TAMS was 0.0194 mol/L.The critical concentration of TAMS can be explained by the maximum amounts of primary amino groups,which can totally react with PP-g-MAH on the surface of SiO_(2)-NH_(2),when the silane monolayer is formed.The synthesized PP-g-SiO_(2)with different molecular weights was mixed with PP by solution mixing to form a series of nanocomposites.The crystallization temperature(T_(c))of nanocomposites increased significantly with the particle loading.The PP-g-SiO_(2) with high molecular weight of grafted chains exhibits a high nucleation ability at 1 wt%nanoparticle loading in PP/PP-g-SiO_(2)nanocomposites.In summary,we provide an effective method to synthesize the well-defined PP-g-SiO_(2)with controlled grafting density,which shows excellent nucleation ability.

A Facile Method to Form a Densely Grafted PEO-b-P4VP Brush on Gold Surface

Here we report a facile method for the preparation of a PEO113-b-P4VP93 brush on gold surface with a grafting density as high as 1.32 chains/nm2; the P4VP blocks were physically adsorbed on gold surface forming an inner layer while the PEO blocks stretched towards the solution forming PEO brush. PEOl13-b-P4VPq3 micelles with P4VP core and PEO shell formed in methanol/water mixed solvents were used as the precursor. By adsorbing PEOII3-b-P4VP93 micelles from pure water, in which the density of the micelles is the largest, maximum amount of the micelles was adsorbed onto gold surface, and the adsorbed micelles existed as individual domains on the surface To prepare the polymer brush with a density as high as possible, we annealed the adsorbed micelles by metha- nol/water mixed solvent at the volume fraction of methanol （VF） of 20%, which was the proper proportion at which the core-forming P4VP chains began to be flexible but the integrity of the micelles was remained. At this volume fraction, almost all the adsorbed micelles originally existing as individual domains were transformed into a dense polymer brush.