The term “soft matter” applies to a variety of physical systems, such as liquids, colloids, polymers, foams, gels, and granular materials. The most fascinating aspect of soft matter lies in the fact that they are not atomic or molecular in nature. They are instead macromolecular aggregates, whose spatial extent lies in the domain 1 nm to 1 ¹m. Some of the most important examples of soft matter are polymers, which exhibit intriguing and useful physical properties. In this work, the adsorption and self assembly of linear and star polymers on smooth surfaces are studied using coarse-grained, bead-springmolecular models and Langevin dynamics computer simulations. The aim is to gain insight on atomic-forcemicroscopy images of polymer films on mica surfaces, adsorbed from dilute solution following a good solvent-to-bad solvent quenching procedure. In the case of linear polymers, under certain experimental conditions, a bimodal cluster distribution is observed. It is demonstrated that this type of distribution can be reproduced in the simulations, and rationalized on the basis of the polymer structures prior to the quench. In addition to providing insight on experimental observations, the simulation results support a number of predicted scaling laws such as the decay of the monomer density as a function of distance from the surface, and the scaling of the filmheight with the strength of the polymer-surface interactions. Star polymers represent a special class of polymers, in which one end of each linear chain is tethered to a small central core to forma single particle. The discovery of these molecules led to the synthesis of a wide range of new materials. Their structures are effectively considered as intermediate between those of colloids and linear polymers. We explore the behaviour of the star polymers (which are like “soft colloids”) in the proximity of a surface, using Langevin dynamics simulations. A number of different measurements such as the height, radius of gyration, and asphericity of adsorbed stars with different number of arms, are shown to provide valuable insights on experimental findings. The simplest soft matter systems consist of spherical, rigid colloidal particles. Examples of such particles are chemically synthesized polystyrene or silica particles. We investigated the neighbour distribution in a two-dimensional polydisperse harddisk fluid, corresponding physically to a colloidal monolayer. The disk diameter distribution was defined by a power-law with the aim of realizing a scale-free nearneighbour network. Scale-free (power-law) behaviour is found in many important networks, for example, in transportation systems, biochemical reactions, scientific and movie-actor collaborations, and sexual contacts. We have provided the first example of a scale-free network in amodel condensed-matter system. Finally, we use genetic algorithms, a method for efficiently searching for minima on energy landscapes, to investigate the ordered equilibrium structures formed by binary mixtures of anisotropic dipolar particles confined on a plane, under the presence of an external magnetic field. The anisotropy of the interparticle forces is controlled by tilting the external magnetic field with respect to the plane. Initially, as the field is tilted the structures are only slightly perturbed, but once the anisotropy exceeds a critical value, completely new structures emerge.

Thesis advisor: Larry W. McLaughlin / There are two major goals for my project. The first is to create and characterize metal-ligand-DNA complexes that could be synthesized using traditional organic methods followed by solid phase techniques. The second is to demonstrate that these complexes with complementary DNA sequences could self-assemble into higher-ordered structures. In order to generate supramolecular DNA-metal structures such as cubic lattices, it is necessary to create an octahedral metal-ligand center tethering six DNA arms as a building block. The Iron/Ru (II) bis(2,2':6',2''terpyridine) derivatives were chosen because: (i) the complex is well known to present octahedral geometry; (ii) the coordination is very stable; and (iii) while previous work required the solid-phase synthesis of six DNA arms simultaneously--an inefficient process--by using terpyridine ligands we need only extend three arms at once. Thus, several terpyridine-linker compounds were synthesized via two different routes. A DNA 14mer was synthesized afterwards by "Reverse Coupling Protocol" on a solid phase synthesizer and the terpyridine was connected to it followed by elongation of the rest two DNA arms. The DNA-terpyridine complexes were evaluated by stepwise hybridization tests and gel electrophoresis with or without the assistance of radio labeling. In addition, the assembly of metal with the terpyridine-DNA complex was also characterized by adding different metal ions such as Iron (II) and Ru (II) to the complex. Various buffer conditions were applied in constructing those conjugates in order to help forming branched DNA-ligand-metal complexes with higher molecular weight. / Thesis (MS) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

This thesis describes the synthesis and coordination chemistry of self-assembled multidentate iron(II) phosphine complexes. Chapter 1 introduces the background to phosphine ligands, their properties, interactions with transition metals and applications. The chapter then discusses macrocyclic and medium ring P,N-containing ligands, as well as some water soluble phosphines. The chapter also introduces the novel self-assembled macrocyclic phosphine complex [FeL1(H2O)2]SO4 (1) and its tetradentate cyclic phosphine ligand L1. Chapter 2 describes the synthesis of [FeL1(H2O)2]SO4 (1) and its coordination chemistry with a variety of ligands, including halides, pseudo-halides, and CO. 57Fe labelled versions of complex 1 and the related dicarbonyl complex [FeL1(H2O)2]SO4 (9) were synthesised as models for the hydrogenase protein Hmd in a Nuclear Resonance Vibrational Spectroscopy study. Reactions were also undertaken to functionalise the hydroxymethyl groups in order to alter the properties of the complexes. The reaction of 1 with acetic anhydride afforded complex [Fe(L2)(k2-O2SO2)] (13), possessing the acylated ligand L2 and a coordinated sulfate ligand. The coordination chemistry of 13 was explored with a variety of neutral and anionic ligands, including halides, pseudohalides, carbonate, and CO. Electrochemical cyclic voltammetric investigations of L1 and L2 complexes were also explored. Chapter 3 reports the investigations carried out to explore the effect of altering the reagents of the self-assembly reaction. The self-assembly reaction to synthesise complex 1 was also attempted with copper(II), nickel(II), copper(II) and zinc(II) salts, as well as in the absence of a metal template, which all did not lead to the formation of any isolable species. The syntheses of the novel iron(II) complexes [Fe(L3)2(SO4)] (23) and cis-[Fe(L3)2Cl2] (24a) containing the new bidentate phosphine ligand L3 are also reported, as well as the coordination chemistry of 24a with a variety of ligands. The reaction of 24a with NaBH4 gave the trans hydride-chloride complex trans-[Fe(L3)2(H)Cl] (29). Electrochemical investigations of the L3 complexes were also carried out. Chapter 4 provides the experimental details for the reactions described in chapters 2 and 3.

The use of low-molecular weight peptide-based hydrogelators (LMWGs) for the immobilisation of enzymes is presented in this thesis. Low-molecular weight hydrogelators are a class of materials which are highly suitable for increasing enzyme lifetimes as they create a suitable biomimetic environment. Immobilised enzymes can be utilised in enzyme fuel cells, providing low-energy conversion routes for chemical processes. The hydrogels also possess tunable properties which allow their structure to be manipulated to give desirable properties. This work begins with an exploration of dipeptide hydrogelators by investigating the effect of varying salt solutions and concentrations of dipeptide on final hydrogel structures. A wide range of characterisation techniques are employed to provide information about the micro- and macro-structure of the hydrogels. The creation of dipeptide hydrogel materials via an electrochemical method is explored, which allows the production of nanometre thick, membrane-like materials. These layers are measured using Surface Plasmon Resonance techniques. The electrochemical technique for dipeptide gelation is expanded in later chapters to produce a range of novel materials. Finally, an exploration into the effect of additives on dipeptide hydrogels is conducted, where the effect of adding chiral molecules is investigated. This provides interesting information regarding the self-assembly processes involved with hydrogelation processes, which has important implications for studying the folding and unfolding processes of peptides.

Small diameter vascular grafts comprised entirely from cells and cell-derived extracellular matrix (ECM) have shown promise in clinical trials and may have potential advantages as in vitro vascular tissue models. A challenge with current cell-derived tissue engineering approaches is the length of time required to generate strong, robust tissue. There is a lack of alternative methods to rapidly assemble cells into a 3D format without the support of a scaffold. Toward the goal of engineering a new approach to rapidly synthesizing vascular tissue constructs entirely from cells, we have developed and characterized a strategy for creating cell-derived tissue rings by cellular self-assembly. The focus of this thesis was to develop the system to rapidly generate engineered tissue rings, and to evaluate their structural and functional properties. To generate tissue rings, rat smooth muscle cells (SMCs) were seeded into round-bottomed, ring-shaped agarose wells with varying inner post diameters (2, 4, and 6 mm). Within 24 hours of seeding, cells aggregated, contracted, and formed robust tissue that could be removed from their wells and handled. If kept in culture, the thickness of these tissue rings increased with time. Mechanical analysis of the tissue showed that it was stronger after only 8 days in culture than engineered tissues generated by other approaches (such as seeding cells in biopolymer gels) cultured and tested at similar time points. Histological staining of the tissue rings revealed high cell densities throughout, along with the presence of glycosaminoglycans and some collagen. We also found that we could use the tissue rings as building blocks to generate larger tubular structures. Briefly, tissue rings were removed from the agarose wells and transferred onto silicone tubing mandrels. Once the rings were placed in contact with each other on the mandrel, they were cultured to allow the rings to fuse together. We found that the ability of tissue rings to fuse decreased with increasing ring “pre-culture� duration, and that we were able to generate fully fused tissue tubes in as little as 8 days (with only one day of ring pre-culture and seven days of fusion). In the last section of this thesis, we established the feasibility of using primary human SMCs to generate self-assembled tissue rings, similar to the self-assembled rings generated with rat SMCs. Compared to the rat SMC rings, human SMC rings were stronger, stiffer and appeared to contain increased levels of collagen. These data showed that human SMCs are capable of self-assembling into tissue rings similar to rat SMCs, and may therefore be used to create engineered human vascular tissue. Overall, we have developed a platform technology that can be used to screen the effects of culture parameters on the structure, mechanics, and function of vascular tissue. We anticipate that through the use of this technology, we can further improve vascular grafts by better understanding factors which promote ECM synthesis and SMC contraction. We can use these results directly toward the generation of vascular grafts by fusing self-assembled cell rings together to form tissue tubes. These novel bioengineered vascular tissues may also serve as a method to produce in vitro models to help further our understanding of vascular diseases, as well as facilitate pre-clinical screening of vascular tissue responses to pharmacologic therapies.

Many emerging technologies would greatly benefit from reliable methods for the production of functional materials with well-defined 3D nanoscale structure. Conceptually, approaches to produce such architectures are divided into two broad classes; top down and bottom up manufacture. In the top down approach, nanoscale structure is created through the controlled removal of material from a bulk starting object. Top down methods have a proven record of reliability in the fabrication of extended two dimensional arrays with fine control over nanoscale features. However, such approaches become increasingly cumbersome when attempting to define structure in three dimensions rather than two. Bottom up methods promise a more reliable route to the formation of such materials. Here, molecular scale building units self-assemble to form a desired structure, driven by pre-defined interactions between individual motifs. Due to the highly specific molecular recognition properties of nucleic acids, along with their relatively simple synthesis and wide range of potential chemical modifications, DNA nanotechnology is now regarded as a prime route for the bottom up fabrication of nanostructured materials. However, current approaches to the formation of designed 3D DNA crystals are complicated by the difficulties in designing sub-units able to assemble in a predictable fashion over length-scales orders of magnitude larger than themselves. Amphiphiles are able to self-assemble into a variety of 3D crystalline phases driven by the frustrated micro-phase separation of hydrophobic and hydrophilic domains, with the structural properties reliant primarily on overall topology of the molecules rather than their exact chemical and geometrical features. Although the mechanism underlying amphiphile self-assembly is robust, it inherently limits control over the fine-scale structural details. This thesis reports on a new class of self-assembling DNA motifs; amphiphilic cholesterol-functionalised DNA nanostars, \emph {C-stars}. C-stars combine key advantages of all-DNA motifs and conventional amphiphilic molecules -- allowing for the preparation of expanded crystalline frameworks with tunable properties and embedded functionality.

Nanoscale colloids and nanoparticles (NPs), have recently emerged as a new class of materials that possess photonic, plasmonic, and/or catalytic emergent properties. However, methods for their rational fabrication into materials with designed structural organization remain to be established. Self-assembly -- the idea that NPs can find each other and spontaneously form a targeted macroscale structure with prescribed microscale organization -- is attractive in this context, particularly because it potentially lends itself to facile, large-scale manufacturing. Such a process, however, relies on a combination of interactions and shape effects for the formation of ordered long-range morphologies and a detailed molecular understanding of the governing physics for these systems remains an open question. In an attempt to reduce the complexity of such systems, a major thrust has been to use two NP sub-populations grafted with complementary single stranded DNA (DNA-NPs). The base pairing of these strands drives their spontaneous organization into crystalline arrays. DNA-mediated self-assembly provides a powerful tool to experimentally realize three dimensional crystalline ordering of NP networks; however, the majority of works within this field have focused on an isotropic, purely attractive interaction motif. While successful in controlling NP ordering, the usage of such symmetric designs severely restricts the range of accessible morphologies. This thesis systematically addresses the various limitations imposed by such a design strategy through both theoretical modeling of DNA-NPs interactions and inverse design of optimized self-assembly building blocks. We first relax the assumption that enthalpy completely dominates self-assembly by directly accounting for the effects of chain-chain repulsion as well as entropic frustrations that results from varying the mixing stoichiometry. We then build in the effect of utilizing anisotropy as a structural motif through the development of a scaling theory that captures the interplay between the chain dynamics and local curvature that results in the formation of non-trivial anisotropic coronas. The effects of anisotropy on both the local morphology and long-range crystalline ordering can then be model through the usage of mean-field and perturbation theories. The resulting composite model enables us to directly study how nano-scale phenomena drive micron-scale self-assembly. Lastly, theoretical developments are combined with a genetic algorithm optimization process into an inverse design framework that allows for an a priori design of molecular building blocks such that they spontaneously pack into any desired lattice morphologies. This strategy serves to address the long-standing challenge of nanomaterials design where one can take arbitrary nano-scale objects and arrange them into desired three-dimensional lattices that posses interesting, emergent properties.

In Chapter 1-3, properties and applications of block copolymers, synthetic methods especially living anionic polymerization as well as the development of the SAAP concept with some of previous successful examples are reviewed. Experimental methods, including the design and establishment of a special high-vacuum system, size exclusion chromatography and laser light scattering, are explained. / In Chapter 4, living anionic polymerization of alpha,o-di bromobutyl end-capped PI-b-PS-b-PI triblock copolymers and the end-capping reaction with 1,4-dibromobutane at the end of polymerization are described, including a in-depth analysis of the reaction mechanism that involves the dimerization of two living oligomer chain during the reaction of living polymeric anions with haloalkanes, i.e., the Wurtz-type coupling reaction. The self assembly and coupling reaction of 1,4-dilithio-1,1,4,4-tetraphenylbutane (DD2-) in n-hexane to form long (PI- b-PS-b-PI)10 multiblock chains are discussed. The coupling efficiencies with and without the self assembly are compared to demonstrate the principle of SAAP. However, the coupling reaction with dianion linker is troublesome because a trace amount of impurities in the solvent can remove its activity. / In Chapter 5, a method of improving the coupling efficiency is described. In this method, PI-b-PS-b-PI triblock copolymers is end-capped with avo-dicarboxylic acid groups via a reaction between living anions and carbon dioxide. Such prepared HOOC-ISI-COOH chains can be coupled with 1,6-hexamethylenediamine (HDA) in the presence of 1,3-dicyclohexylcarbodiimide (DCC) after the self assembly. The size exclusion chromatography (SEC) analysis shows that the SAAP method mainly leads to the formation of triblock copolymer chain dimers and the coupling efficiency is close to 50%. There is no coupling in THF without the self assembly. Further, a much better method of using alpha,o-diacyl chloride end-capped PI-b-PS-b-PI triblock copolymer chains in SAAP to prepare long multiblock copolymer chains is described. Using this recently developed method, we are able to prepared long ∼90-block copolymer chains (PI-b-PS-b-PI)30 which clearly shows the advantage of using SAAP to prepare long multiblock copolymers with a controllable sequence and different block lengths. / In this thesis, we have proposed and developed a novel method: The Self-Assembly Assisted Polypolymerization (SAAP). Namely, using the self-assembly of A-B-A triblock copolymers with two active end groups in a selective solvent for the A-block to concentrate and expose the active end groups on the periphery of the resultant core-shell polymeric micelles, we can effectively couple each two active ends on different chains together to form a long multiblock copolymer chain with its sequence and block length well controlled by the initial triblock copolymer. To accomplish this project, we first built a high-vacuum system for living anionic polymerization and then synthesized and characterized narrowly distributed polyisoprene-b-polystyrene- b-polyisoprene (PI-b-PS-b-PI) triblock copolymer chains with their both ends capped respectively with bromobutyl and carboxylic acid active groups. The self assembly of such prepared triblock copolymers in n-hexane, a selective solvent for PI, was studied by a combination of static and dynamic laser light scattering (LLS). Finally, the self-assembled end-functionalized PI-b-PS-b-PI chains were coupled together by difunctional small molecules (linkers) to form long multiblock copolymers with a controlled structure. / Hong, Liangzhi. / "Aug 2007." / Adviser: Chi Wu. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1036. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese. / School code: 1307.

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Les polymères biomimétiques incorporant des groupes zwitterioniques mimant la phosphatidylcholine, comme par exemple la phosphobétaïne, la sulfobétaïne ou encore la carboxybétaïne, ont reçu une attention grandissante pour une utilisation dans la prochaine génération de matériaux en contact avec le sang, grâce à leur excellentes propriétés anti-bioadhésives. Le poly(methacrylate de sulfobétaïne) (polySBMA), avec un squelette methacrylate et un analogue de la taurine bétaïne (CH2CH2N+(CH3)2CH2CH2CH2SO3-) comme groupe pendant, est de loin le polymère le plus étudié en raison de sa relative facilité de préparation. Il est maintenant admis que les brosses polymères recouvrant une surface de groupes zwitterioniques permettent l'obtention d'une surface résistance à l'adsorption de biocomposants, permettant d'envisager une application potentielle pour des matériaux mis en contact du sang, comme les implants par exemple. Dans cette thèse, la nouvelle fonctionnalisation de copolymères dérivés du sulfobétaïne et leurs potentielles applications sont développées et étudiées.Dans une première partie, des copolymères diblocs « schizophréniques » contenant des blocs nonioniques et zwittérioniques ont été préparés pour différentes masses molaires via la polymérisation radicalaire contrôlée (ATRP : atom-transfer radical polymerization). Dans ce travail nous présentons une étude systématique de la relation entre la conformation des chaînes copolymères en solution et leur impact sur l'hémocompatibilité dans une solution de sang humain. Le comportement « schizophrénique » de copolymères PNIPAAm-b-PSBMA a été observé par RMN 1H, diffusion dynamique de la lumière et turbidité, démontrant ainsi une double transition morphologique avec à la fois une LCST (lower critical solution temperature) et une UCST (upper critical solution temperature) en solution aqueuse. En dessous de l'UCST du bloc PSBMA, des micelles sont obtenues avec un cœur insoluble de PSBMA entouré d'une écorce soluble de PNIPAAm alors que la structure inverse est observée au-dessus de la LCST du bloc PNIPAAm. Entre l'UCST et la LCST, des unimères parfaitement solubles ont été détectés. La taille hydrodynamique des copolymères et des homopolymères correspondants a également permise de corréler directement la morphologie micellaire avec la compatibilité avec du sang humain. L'adsorption isolée de fibrinogènes humains sur le copolymère à bloc a été étudiée par DLS pour déterminer la stabilité de la résistance à la bio-adhésion d'une suspension de copolymères. Le PNIPAAm-b-PSBMA a démontré une activité anti-coagulante et anti-hémolytique extrêmement élevées sur une large gamme de température allant de 4 à 40°C. La non-dépendance de la biocompatibilité à la température, associée au comportement schizophrénique en solution aqueuse, nous a amené à réfléchir à d'éventuelles applications.Dans la seconde partie de ce manuscrit, des copolymères diblocs « intelligents » contenant des blocs ioniques et zwittérioniques ont été préparés par polymérisation radicalaire contrôlée de type RAFT (reversible the addition-fragmentation chain transfer). Dans ce travail, nous présentons une étude systématique sur la formation d'un nouveau vecteur d'ADN à partir d'un coeur polyplexe ADN/ poly(dimethylaminoethyl methacrylate) (PDMAEMA), recouvert, via des interactions électrostatiques, de copolymères poly(acide acrylique)-block-poly(méthacrylate de sulfobétaïne) (PAA-b-PSBMA). Son impact sur l'hémocompatibilité ainsi que sur l'efficacité de la transfection de gènes ont été vérifiés, en prenant comme référence des polyplexes formés à partir de polyethyleneimine (Pei). La capacité d'interaction des plasmides ADN avec le Pei, PDMAEMA, et PAA-b-PSBMA a été évaluée par « ethidium bromide displacement assays » et « agarose gel retardation assays » en fixant le rapport en atomes d'azote de polymère par atomes de phosphore des nucléotides (rapport N/P) ainsi que le pH de la solution. La mesure du temps de coagulati / Biomimetic polymers containing zwitterionic structures poly(sulfobetaine methacrylate) (polySBMA) has become the most widely studied zwitterionic polymer due to its easy of synthetic preparation. It is now recognized that grafted dense polymer brushes, composed of zwitterionic polySBMA, formed an effective and stable nonfouling surface, potentially enabling the practical use in human blood-contacting devices and implants. In this dissertation, the new functionalization of zwitterionic sulfobetaine-based copolymers and their potential biomedical applications was developed and investigated. In the first part of the dissertation, “schizophrenic” diblock copolymers containing nonionic and zwitterionic blocks were prepared with well-controlled molecular weights via the atom-transfer radical polymerization (ATRP). In this work, we demonstrate a systematic study of how morphological changes of poly(N-isopropylacrylamide)-block-poly(sulfobetaine methacrylate) (PNIPAAm-b- PSBMA) copolymers affect hemocompatibility in the human blood solution. The “schizophrenic” behavior of PNIPAAm-b-PSBMA was observed by 1H nuclear magnetic resonance (1H NMR), dynamic light scattering (DLS), and turbidity measurement with double morphological transition, exhibiting both lower critical solution temperature (LCST) and upper critical solution temperature (UCST) in aqueous solution. Human fibrinogen adsorption onto the PNIPAAm-b-PSBMA copolymers from single-protein solutions was measured by DLS to determine the nonfouling stability of copolymer suspension. The new nonfouling nature of PNIPAAm-b-PSBMA copolymers was demonstrated to show an extremely high anticoagulant activity and antihemolytic activity in human blood over a wide range of explored temperatures from 4 ºC to 40 ºC and suggests their potential in blood-contacting applications.In the second part of the dissertation, “intelligent” diblock copolymers containing ionic and zwitterionic blocks were prepared with well-controlled molecular weights via reversible the addition-fragmentation chain transfer (RAFT) polymerization. In this work, we demonstrate a systematic study of how zwitterionic shielding on a new self-assembled cargo of plasmid DNA/poly(dimethylaminoethyl methacrylate) (PDMAEMA) polyplexes conjugated with poly(acrylic acid)-block-poly(sulfobetaine methacrylate) (PAA-b-PSBMA) copolymers affect hemocompatibility in human blood solution and gene transfection onto target cells. The carrier stability, cell toxicity, hemocompatibility, and gene transfection efficiency of DNA/ PDMAEMA/PAA-b-PSBMA polyplexes was investigated as compared with DNA/polyethyleneimine (PEI)/PAA-b-PSBMA. Hemocompatibility of the prepared polyplexes was evaluated by the anticoagulant activity of the blood coagulant determined by testing the plasma-clotting time and the antihemolytic activity in human blood by measuring red blood-cell hemolysis. The pH-dependent gene transfection of DNA/ PDMAEMA/PAA-b-PSBMA polyplexes, along with their stimuli-responsive behavior, suggests their potential in blood-contacting gene delivery applications.In the final part of the dissertation, ionic/zwitterionic PAA-b-PSBMA diblock copolymer was extended to prepare anti-fouling poly(ether imide) membranes with well-controlled nano-pore structures and water flux via layer-by-layer self-assembled coating process. The surface charge property of the prepared membrane can be regulated by PEI/PAA ratios. Low protein-fouling membrane surfaces from BSA and fibrinogen solution with respect to uncoated membrane surfaces are achieved with optimized block ratio of PAA and PSBMA. Thus, positively charged membranes, coated with zwitterionic copolymers containing anionic groups via charge-driven, are ideal for highly resisting protein adsorption if the membrane surface density of the zwitterionic groups is controlled to a high-level densities.