Zwitterionic Brushes Research Articles

Bioactive zwitterionic polymer brushes grafted from silicon wafers via SI-ATRP for enhancement of antifouling properties and endothelial cell selectivity

Zwitterionic copolymers keep good resistance to platelet adhesion and nonspecific protein adsorption. In this study, A block copolymer brushes consisting of carboxybetaine methacrylate (CBMA) and glycidyl methacrylate (GMA) were grafted from silicon wafers via surface-initiated atom transfer radical polymerization, and then the Arg-Glu-Asp-Val (REDV) peptide was attached to the polymer brush via an reactive epoxy group of the P(GMA) unit to improve endothelial cells (ECs) selectivity. These modified surfaces were evaluated with scanning electron microscopy, atomic force microscopy, attenuated total reflectance-Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and static water contact angle measurement. The results showed that REDV-modified zwitterionic brushes were successfully constructed on silicon wafers. The biocompatibility of the membrane was determined by plasma recalcification time assay and platelet adhesion test. The results showed that the modified substrate exhibited good blood compatibility. Moreover, the proliferation of ECs and smooth muscle cells onto the REDV-modified copolymer brushes were examined to demonstrate the synergistic effect of CBMA with antifouling property and REDV peptide with ECs selectivity. All assays showed that the silicon wafers displayed excellent EC selectivity after modification. In summary, REDV-modified zwitterionic brushes had great potential for cardiovascular stent implantation.

Comparison of organic fouling resistance of thin-film composite membranes modified by hydrophilic silica nanoparticles and zwitterionic polymer brushes

We conducted a comparative study to investigate the efficacies of two different types of highly hydrophilic materials (i.e., silica nanoparticles (SiNPs) and zwitterionic polymers) for antifouling surface modification of polyamide thin-film composite (TFC) membranes. Dense layers of SiNPs and zwitterionic polymer brushes were grafted on the membrane surfaces via dip-coating with aminosilane-functionalized SiNPs (i.e., SiNP-TFC membrane) and surface-initiated atom-transfer radical-polymerization of sulfobetaine methacrylate (i.e., PSBMA-TFC membrane), respectively. With the same degree of enhancement of surface hydrophilicity and identical surface roughness, the PSBMA-TFC membrane exhibited significantly higher fouling resistance than the SiNP-TFC membrane in adsorption tests of proteins and bacteria as well as in forward osmosis (FO) dynamic fouling experiments using alginate as a model organic foulant. Chemical force microscopy measurements revealed that membrane-foulant electrostatic attraction aggravates organic fouling of the SiNP-TFC membrane to a certain degree, but the primary fouling mechanism is the complexation of organic foulants with carboxylic groups on the polyamide membrane surface. We attribute the lower fouling resistance of the SiNP-TFC membrane to the high density of surface carboxylic groups that may still be accessible to foulants as well as to membrane-foulant electrostatic interaction. On the contrary, the zwitterionic polymer brushes effectively shield the surface carboxylic groups and provide steric hindrance against foulant adsorption due to significant hydration of the zwitterionic brushes.

Anti-Fouling Double-Skinned Forward Osmosis Membrane with Zwitterionic Brush for Oily Wastewater Treatment

Despite its attractive features for energy saving separation, the performance of forward osmosis (FO) has been restricted by internal concentration polarization and fast fouling propensity that occur in the membrane sublayer. These problems have significantly affected the membrane performance when treating highly contaminated oily wastewater. In this study, a novel double-skinned FO membrane with excellent anti-fouling properties has been developed for emulsified oil-water treatment. The double-skinned FO membrane comprises a fully porous sublayer sandwiched between a highly dense polyamide (PA) layer for salt rejection and a fairly loose dense bottom zwitterionic layer for emulsified oil particle removal. The top dense PA layer was synthesized via interfacial polymerization meanwhile the bottom layer was made up of a zwitterionic polyelectrolyte brush - (poly(3-(N-2-methacryloxyethyl-N,N-dimethyl) ammonatopropanesultone), abbreviated as PMAPS layer. The resultant double-skinned membrane exhibited a high water flux of 13.7 ± 0.3 L/m2.h and reverse salt transport of 1.6 ± 0.2 g/m2.h under FO mode using 2 M NaCl as the draw solution and emulsified oily solution as the feed. The double-skinned membrane outperforms the single-skinned membrane with much lower fouling propensity for emulsified oil-water separation.

Surface modification of silicon wafer by grafting zwitterionic polymers to improve its antifouling property

Silicon (111) wafer was modified by triethoxyvinylsilane containing double bond as an intermedium, and then P4VP (polymer 4-vinyl pyridine) brush was “grafted” onto the surface of silicon wafer containing reactive double bonds by adopting the “grafting from” way and Si-P4VP substrate (silicon wafer grafted by P4VP) was obtained. Finally, P4VP brush of Si-P4VP substrate was modified by 1,3-propanesulfonate fully to obtain P4VP-psl brush (zwitterionic polypyridinium salt) and the functional Si-P4VP-psl substrate (silicon wafer grafted by zwitterionic polypyridinium salt based on polymer 4-vinyl pyridine) was obtained successfully. The antifouling property of the silicon wafer, the Si-P4VP substrate and the Si-P4VP-psl substrate was investigated by using bovine serum albumin, mononuclear macrophages (RAW 264.7) and Escherichia coli (E. coli) ATTC25922 as model bacterium. The results showed that compared with the blank sample-silicon wafer, the Si-P4VP-psl substrate had excellent anti-adhesion ability against bovine serum albumin, cells and bacterium, due to zwitterionic P4VP-psl brush (polymer 4-vinyl pyridine salt) having special functionality like antifouling ability on biomaterial field.

HILIC Stationary Phase Based on Monodisperse-Porous Polymethacrylate Beads Functionalized with Zwitterionic Molecular Brushes

Zwitterionic molecular brushes were generated on monodisperse-porous poly(3-chloro-2-hydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(HPMA-Cl-co-EDMA) beads (5.5 μm in size) by surface initiated atom-transfer radical polymerization (SI-ATRP) of ([2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide) (MEDSPAH) via three different chemical routes. In the first route, triethanolamine was used as a spacer arm for attachment of surface initiator and SI-ATRP was initiated by chlorine moiety attached onto the spacer arm. In the second route, ethylenediamine was used as spacer arm and SI-ATRP was initiated with bromine moiety attached onto the spacer arm. In the third one, SI-ATRP was directly initiated with the chlorine moiety of HPMA-Cl units of the beads without using a spacer arm. Poly(MEDSPAH) brushes with the highest surface concentration and the shortest chain length were generated on the polymer beads by an SI-ATRP process initiated with bromine attached onto the surface with the spacer arm. The formation of higher amount of molecular brush with the shorter chain length was explained by higher radical generation rate of bromine as the surface initiator. Poly(MEDSPAH)-grafted poly(HPMA-Cl-co-EDMA) beads produced with different chemical routes were utilized as stationary phase for the separation of polar analytes in HILIC mode. Better chromatographic separations were obtained with the stationary phase carrying zwitterionic molecular brushes with the longest chain length. Chain length of the zwitterionic ligand was also more effective with respect to its surface concentration for better separation of nucleosides, nucleotides, acrylic compounds, and organic acids in HILIC mode.

Antifouling Thin-Film Composite Membranes by Controlled Architecture of Zwitterionic Polymer Brush Layer.

In this study, we demonstrate a highly antifouling thin-film composite (TFC) membrane by grafting a zwitterionic polymer brush via atom-transfer radical-polymerization (ATRP), a controlled, environmentally benign chemical process. Initiator molecules for polymerization were immobilized on the membrane surface by bioinspired catechol chemistry, leading to the grafting of a dense zwitterionic polymer brush layer. Surface characterization revealed that the modified membrane exhibits reduced surface roughness, enhanced hydrophilicity, and lower surface charge. Chemical force microscopy demonstrated that the modified membrane displayed foulant-membrane interaction forces that were 1 order of magnitude smaller than those of the pristine TFC membrane. The excellent fouling resistance imparted by the zwitterionic brush layer was further demonstrated by significantly reduced adsorption of proteins and bacteria. In addition, forward osmosis fouling experiments with a feed solution containing a mixture of organic foulants (bovine-serum albumin, alginate, and natural organic matter) indicated that the modified membrane exhibited significantly lower water flux decline compared to the pristine TFC membrane. The controlled architecture of the zwitterionic polymer brush via ATRP has the potential for a facile antifouling modification of a wide range of water treatment membranes without compromising intrinsic transport properties.

Self-assembling characteristics of amphiphilic zwitterionic brush random copolymers at the air–water interface

Amphiphilic zwitterionic brush random copolymers bearing sulfobetaine groups at the bristle ends underwent segregation at the air–water interface, always forming only the Langmuir monolayer structure rather than any other structures.

Zwitterionic modification of polyurethane membranes for enhancing the anti-fouling property

Polyurethane (PU) is a biopolymer that has been commonly used for biomedical applications. However, the biofouling phenomenon on the hydrophobic PU surface is one of the crucial issues that embarrassing its applications. Here, we report a facile & efficient approach to improve the anti-biofouling ability of the PU substrates. Active residues were firstly generated on the PU surface by using the low temperature air-plasma treatment, promoting the immobilization of the atom transfer radical polymerization (ATRP) initiators on the surface. Then, three types of zwitterionic polymer brushes, as well as PEG brushes, have been fabricated on the PU substrates through surface-initiated ATRP (SI-ATRP). Robust surface characterizations that capable of revealing the surface chemistry (including X-ray photoelectron spectroscopy (XPS) and wettability tests), and antifouling evaluations of the PU substrates (protein adsorption, platelet adhesion, and cell adhesion measurements) were performed. Results showed that three types of zwitterionic brushes have been successful grafted on the PU surface, respectively. And the three types of zwitterionic brushes, in general, significantly inhibited the protein adsorption, the platelet adhesion, and the cell adhesion on the PU surface, endowing a significantly improved anti-fouling ability to the PU substrates. Furthermore, we found that this facial zwitterionic surface modification did not compromise the mechanical property of the PU substrates. This strategy could be easily exploited to PU-based biomaterials to improve their performance in many applications.

Anti-fouling behavior of polymer brush immobilized surfaces

Nature-inspired material design concepts and recent progress on anti-fouling polymer materials are reviewed, and our recent researches on anti-fouling studies with polymer brushes are summarized. Zwitterionic polyelectrolyte brush immobilized surfaces represent significant anti-fouling for bio-macromolecules, oil foulants, marine fouling organisms and pipeline foulants. The anti-fouling mechanism was considered on the basis of the wetting, lubrication, hydrated chain dimension and hydrogen-bonding structure of hydrated water in the polyelectrolyte brushes.

Development of polypeptide-based zwitterionic amphiphilic micelles for nanodrug delivery.

Protein molecules, which typically have a hydrophobic core and a zwitterionic shell with a polypeptide backbone, could be ideal materials for nanodrug vehicles (NDVs) with low side effects. Here, we synthesized poly(l-aspartic acid(lysine))-b-poly(l-lysine(Z)) (PAsp(Lys)-b-PLys(Z)) (PALLZ), a novel amphiphilic block polypeptide with key structures of protein to investigate the possibility for use as a NDV. This polypeptide can spontaneously self-assemble into micelles in aqueous solution with a zwitterionic brush (the PAsp(Lys) part) to provide the nonfouling shell and a hydrophobic core (the PLys(Z) part) for loading hydrophobic drugs. The doxorubicin (DOX) loaded PALLZ micelles showed excellent resistance to nonspecific protein adsorption in FBS, which leads to very low internalization. Moreover, PALLZ micelles showed no cytotoxicity to MCF7, HeLa and HepG-2 cells up to 500 μg mL-1. All these results indicated that zwitterionic amphiphilic block polypeptides could be promising materials for NDVs.

Synthesis and characterization of a novel, biomimetic, tribologically enhanced hydrogel for biomedical applications

Event Abstract Back to Event Synthesis and characterization of a novel, biomimetic, tribologically enhanced hydrogel for biomedical applications Allen O. Osaheni1, Patrick T. Mather2 and Michelle M. Blum1 1 Syracuse University, Mechanical and Aerospace Engineering, United States 2 Syracuse University, Biomedical and Chemical Engineering, United States Although hydrogels have long been recognized as an attractive candidate for a wide variety of biomedical applications, their use as a synthetic implant in load bearing applications, such as the replacement of damaged menisci or articular cartilage, is severely limited due to their inferior friction and wear properties [1]. Although the presence of zwitterionic brushes have shown tremendous promise for the promotion of boundary lubrication comparable to articular cartilage, the synergistic effects of the functionalization of such polymers to materials that exhibit fluid pressurization mechanism similar to cartilage has yet to be investigated [2][3]. We postulate that blending poly(vinyl alcohol) (PVA) with a zwitterionic polyacrylate prior to gel formation by the freeze-thaw method will result in enhanced surface lubrication due to the strong and pH-independent hydrophilicity of the zwitterionic groups combined with the fluid pressurization mechanism exhibited by the hydrogel. The chemical composition of these tribologically enhanced materials was verified through the use of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) . Coefficient of Friction (COF) experiments performed via tribo-rheometry in DI water yielded as much as an 80% reduction in average COF compared to that unmodified PVA hydrogel. In addition, the blended samples maintained mechanical and physical properties comparable to the control. These results suggest that the dramatic drop in average COF is attributed to a change in the surface interaction between the articulating surfaces due to the zwitterionic boundary lubricant rather than changes to the physical and mechanical properties of the bulk material. Further characterization of these materials involved quantification of the changes in hydrogel microstructure through the use of wide and small angle x-ray scattering as well as assessment of the size and shape of the wear particles produced during the friction experiments through the use of dynamic light scattering and scanning electron microscopy. Finally, hydrogel biocompatibility was accessed through the use of an L929 fibroblasts cell line with an in vitro cytotoxicity assay. Preliminary results suggest that the tribologically enhanced system does not appear to influence the inherent biocompatibility of PVA. Overall, this study introduces a new platform for the design of advanced materials for use as synthetic implants to repair damaged load bearing tissue as well as a variety of other medical applications in which minimizing COF is an attractive feature. Eric Finkelstein; Wenyang Pan; Leah Anderson

Versatile inhibition of marine organism settlement by zwitterionic polymer brushes

The anti-fouling character of polymer brushes against marine organisms was investigated by performing settlement tests with barnacle cypris larvae and mussel larvae in their adhesion period, as well as a marine bacteria colonization test. The surface charge and hydration state in saline seawater appear to be important factors in the versatile anti-fouling performance of zwitterionic polyelectrolyte brushes.

Overview of PES biocompatible/hemodialysis membranes: PES-blood interactions and modification techniques.

Polyethersulfone (PES) based membranes are used for dialysis, but exposure to blood can result in numerous interactions between the blood elements and the membrane. Adsorption and transformation of plasma proteins, activation of blood cells, adherence of platelets and thrombosis reactions against PES membrane can invoke severe blood reactions causing the increase rate of mortality and morbidity of hemodialysis (HD) patients. In order to minimize blood immune response, different biomimetic, zwitterionic, non-ionic, anticoagulant molecules and hydrophilic brushes were immobilized or blended with PES polymers. These additives modified the nature of the membrane, enhanced their biocompatibility and also increased the uremic waste dialysis properties. In this review, current perspectives of the different additives which are used with PES are highlighted in relation with PES membrane-associated blood reactions. The additive's purpose, compatibility, preparation techniques, methods of addition to polymer and influence on the chemistry and performance of hemodialysis membranes are described.

Nanostructure and salt effect of zwitterionic carboxybetaine brush at the air/water interface.

Zwitterionic amphiphilic diblock copolymer, poly(ethylhexyl acrylate)-b-poly(carboxybetaine) (PEHA-b-PGLBT), was synthesized by the reversible addition-fragmentation chain transfer (RAFT) method with precise control of block length and polydispersity. The polymers thus obtained were spread onto the water surface to form a polymer monolayer. The fundamental property and nanostructure of the block copolymer monolayer were systematically studied by the surface pressure-molecular area (π-A) isotherm, Brewster angle microscopy (BAM), and X-ray reflectivity (XR) techniques. The π values of the monolayer increased by compression in relatively larger A regions. After showing a large plateau region by compression, the π value sharply increased at very small A regions, suggesting the formation of poly(GLBT) brush formation just beneath the water surface. The domain structure of μm size was observed by BAM in the plateau region. XR profiles for the monolayer at higher surface pressure regions clearly showed the PGLBT brush formation in addition to PGLBT carpet layer formation under the hydrophobic PEHA layer on the water surface, as was observed for both anionic and cationic brush layer in the water surface monolayer studied previously. The critical brush density, where the PGLBT brush is formed, was estimated to be about 0.30 chains/nm(2) for the (EHA)45-b-(GLBT)60 monolayer, which is relatively large compared to other ionic brushes. This observation is consistent with the fact that the origin of brush formation is mainly steric hindrance between brush chains. The brush thickness increased by compression and also by salt addition, unlike the normal ionic brush (anionic and cationic), whose thickness tended to decrease, i.e., shrink, by salt addition. This might be a character unique to the zwitterionic brush, and its origin is thought to be transition to an ionic nature from the almost nonionic inner salt caused by salt addition since both the cation and anion of the GLBT chain obtained counterions by the addition of salt. This stretching nature of the PGLBT brush depends on the ion species of the salt added, and it followed the Hofmeister series, i.e., more stretching in the order of Li(+) > Na(+) > K(+). However, it was rather insensitive to the anion species (Cl(-), Br(-), SCN(-)), which suggests that the carboxylic anion has a more dominant effect than the quaternized cation in GLBT although the former is a weak acid and the latter is believed to be a strong base.

Ion transport and selectivity in biomimetic nanopores with pH-tunable zwitterionic polyelectrolyte brushes.

Inspired by nature, functionalized nanopores with biomimetic structures have attracted growing interests in using them as novel platforms for applications of regulating ion and nanoparticle transport. To improve these emerging applications, we study theoretically for the first time the ion transport and selectivity in short nanopores functionalized with pH tunable, zwitterionic polyelectrolyte (PE) brushes. In addition to background salt ions, the study takes into account the presence of H(+) and OH(-) ions along with the chemistry reactions between functional groups on PE chains and protons. Due to ion concentration polarization, the charge density of PE layers is not homogeneously distributed and depends significantly on the background salt concentration, pH, grafting density of PE chains, and applied voltage bias, thereby resulting in many interesting and unexpected ion transport phenomena in the nanopore. For example, the ion selectivity of the biomimetic nanopore can be regulated from anion-selective (cation-selective) to cation-selective (anion-selective) by diminishing (raising) the solution pH when a sufficiently small grafting density of PE chains, large voltage bias, and low background salt concentration are applied.

Molecular Design of Antifouling Polymer Brushes Using Sequence-Specific Peptoids.

Material systems that can be used to flexibly and precisely define the chemical nature and molecular arrangement of a surface would be invaluable for the control of complex biointerfacial interactions. For example, progress in antifouling polymer biointerfaces that prevents nonspecific protein adsorption and cell attachment, which can significantly improve the performance of an array of biomedical and industrial applications, is hampered by a lack of chemical models to identify the molecular features conferring their properties. Poly(N-substituted glycine) “peptoids” are peptidomimetic polymers that can be conveniently synthesized with specific monomer sequences and chain lengths, and are presented as a versatile platform for investigating the molecular design of antifouling polymer brushes. Zwitterionic antifouling polymer brushes have captured significant recent attention, and a targeted library of zwitterionic peptoid brushes with different charge densities, hydration, separations between charged groups, chain lengths, and grafted chain densities, is quantitatively evaluated for their antifouling properties through a range of protein adsorption and cell attachment assays. Specific zwitterionic brush designs are found to give rise to distinct but subtle differences in properties. The results also point to the dominant roles of the grafted chain density and chain length in determining the performance of antifouling polymer brushes.

A New Stationary Phase for Hydrophilic Interaction Chromatography: Polyacrylate-Based Hydrophilic, Monosized-Porous Beads with Zwitterionic Molecular Brushes

Hydrophilic, polyacrylate-based, monosized-porous beads with zwitterionic molecular brushes were synthesized as a new stationary medium for hydrophilic interaction chromatography. Monosized-porous poly(glycerol-1,3-diglycerolate diacrylate-co-glycerol dimethacrylate), poly(GDGDA-co-GDMA), beads 5 μm in size were obtained by a staged-shape template polymerization. As an initiator for surface-initiated atom transfer radical polymerization (SI-ATRP), bromine functionality was obtained on the beads by reacting their hydroxyl groups with 3-(aminopropyl)triethoxysilane and α-bromoisobutyryl bromide, respectively. Zwitterionic molecular brushes on the hydrophilic poly(GDGDA-co-GDMA) beads were generated by SI-ATRP of a sulfobetaine monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (MESH). Poly(MESH)-grafted poly(GDGDA-co-GDMA), poly(MESH)g-poly(GDGDAco-GDMA), beads were slurry packed into the microbore columns with 2 mm i.d. and evaluated as stationary medium for the separation of organic acids, nucleosides and peptides using microbore columns in hydrophilic interaction chromatography with the plate numbers up to 30,000 plates m−1.

Modification of Ti6Al4V substrates with well-defined zwitterionic polysulfobetaine brushes for improved surface mineralization.

Osteoconductive mineral coatings are beneficial for improving the osteointegration of metallic orthopedic/dental implants, but achieving adequate structural integration between the surface minerals and underlying metallic substrates has been a significant challenge. Here, we report covalent grafting of zwitterionic poly(sulfobetaine methacrylate) (pSBMA) brushes on the Ti6Al4V substrates to promote the surface-mineralization of hydroxyapatite with enhanced surface mineral coverage and mineral-substrate interfacial adhesion. We first optimized the atom transfer radical polymerization (ATRP) conditions for synthesizing pSBMA polymers in solution. Well-controlled pSBMA polymers (relative molecular weight up to 26kD, PDI = 1.17) with high conversions were obtained when the ATRP was carried out in trifluoroethanol/ionic liquid system at 60 °C. Applying identical polymerization conditions, surface-initiated atom transfer radical polymerization (SI-ATRP) was carried out to graft zwitterionic pSBMA brushes (PDI < 1.20) from the Ti6Al4V substrates, generating a stable superhydrophilic and low-fouling surface coating without compromising the bulk mechanic property of the Ti6Al4V substrates. The zwitterionic pSBMA surface brushes, capable of attracting both cationic and anionic precursor ions during calcium phosphate apatite mineralization, increased the surface mineral coverage from 32% to 71%, and significantly reinforced the attachment of the apatite crystals on the Ti6Al4V substrate. This facile approach to surface modification of metallic substrates can be exploited to generate multifunctional polymer coatings and improve the performance of metallic implants in skeletal tissue engineering and orthopedic and dental care.

Anti-biofouling ability and cytocompatibility of the zwitterionic brushes-modified cellulose membrane.

Blood compatibility and cytocompatibility are key requirements of blood-contacting biomaterials for biomedical applications. Here, we showed the general zwitterionic surface modification of cellulose membrane (CM) substrates, via surface-initiated atom transfer radical polymerization (SI-ATRP), to enhance the anti-biofouling ability without compromising the cytocompatibility of the substrates. Robust X-ray photoelectron spectroscopy (XPS) characterization revealed the successful construction of three zwitterionic brushes, which significantly increased the hydrophilicity of the CM substrates. The zwitterionic brushes-modified CM substrates can significantly reduce the non-specific adsorption of proteins, platelet adhesion and cell attachment, indicating a generally and significantly improved anti-biofouling ability, which is comparable to that of the benchmark anti-fouling poly(ethylene glycol) (PEG) surface. Inspired by the varied in situ cell morphology observed on different substrates, we further investigated the cytocompatibility of the zwitterionic coatings and showed the general cytocompatibility of zwitterionic brush-modified CM surfaces based on both 2D (cell cultured with zwitterionic surfaces) and 3D cell cultures (cell encapsulation in zwitterionic hydrogels). This work provides a promising general approach to enhancing the blood compatibility of cellulose-based materials without compromising their cytocompatibility. The cytocompatibility observation may enrich the perceptions of the zwitterionic modification of substrates and may be beneficial for the in vivo applications of zwitterionic materials.

Surface self-assembled zwitterionization of poly(vinylidene fluoride) microfiltration membranes via hydrophobic-driven coating for improved blood compatibility

A facile surface self-assembled zwitterionization process is presented, aiming at improving the blood compatibility of poly(vinylidene fluoride) (PVDF) membranes. Zwitterionic diblock copolymers containing hydrophobic propylene oxide and hydrophilic sulfobetaine methacrylate blocks were prepared with well controlled molecular weights via atom-transfer radical polymerization (ATRP). Poly(propylene oxide)-block-poly(sulfobetaine methacrylate) (PPO-b-PSBMA) copolymers with varying zwitterionic PSBMA lengths were coated by self-assembling process onto the surface of PVDF microfiltration membranes in order to enhance their surface hydrophilicity and protein resistance. A systematic study regarding the effect of block lengths of PPO-b-PSBMA copolymers on the hemocompatibility of zwitterionic PVDF membranes in human blood solution was then performed. Protein adsorption from single-protein solutions and 100% blood plasma solutions was measured on the PVDF surfaces covered with PPO-b-PSBMA brushes. If the increase in PPO content in copolymer increased the efficiency of coating on the membrane, resistance to human fibrinogen adsorption was enhanced when increasing the PSBMA content. The control of the anchoring structures of zwitterionic copolymer layers highly regulates the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. PVDF membranes coated with PPO-b-PSBMA containing a high amount of zwitterionic SBMA units presented a high hydration capability, believed to allow improving significantly the hemocompatible character of PVDF membranes. This work suggests that the hemocompatible nature of self-assembled zwitterionic brushes gives them a great potential in the molecular design of antithrombogenic membranes for use in human blood applications.