Zwitterionic Monomer Research Articles

A Thermal Thickening System Based on the Self-Assembly of a Zwitterionic Hydrophobic Association Polymer and Surfactant

The zwitterionic monomer, 1-(2-hydroxypropyl-sulfo)-acrylamide ethyl-N,N-dimethyl ammonium chloride (MeSA) was copolymerised with acrylamide (AM), acrylic acid (AA), and a hydrophobic monomer N,N-diallyl oleamide (DNDA) to obtain the zwitterionic hydrophobic association polymer AM/AA/DNDA/MeSA. The structure of the hydrophobic association polymer was characterised by 1H NMR, FT-IR, and intrinsic viscosity studies. The self-assembly system of the polymer and the surfactant Tween-40 was then formed, and the rheological properties and adsorptive performance of the self-assembly system were investigated. The result showed that the polymer–surfactant self-assembly system had good properties such as thickening, temperature resistance, salt resistance, and shear resistance. It is shown that the thermal thickening phenomenon, which allows the system to be used as a good petrochemical product in a high-temperature environment, provides a vital research foundation for the future application of this kind of self-assembly system.

Antibacterial Zwitterionic Polyelectrolyte Hydrogel Adhesives with Adhesion Strength Mediated by Electrostatic Mismatch.

Biotissue adhesives and antibacterial materials have great potential applications in wound dressing, implantable devices, and bioelectronics. In this study, stretchable tissue adhesive hydrogels with intrinsic antibacterial properties have been demonstrated by copolymerizing zwitterionic monomers with ionic monomers. The hydrogels are stretchable to about 900% strain and show a modulus of 4-9 kPa. The zwitterionic moieties provide strong dipole-dipole interaction, electrostatic interaction, and hydrogen bonding with the skin surface, and thus show adhesion strength values of 1-4 kPa to skin. Meanwhile, the copolymerized cationic or anionic monomers break the intrinsic electrostatic stoichiometry of the zwitterionic units and thus mediate the electrostatic interactions and the adhesion strength with the surface. The stretchable hydrogels form a robust and compliant (due to low modulus and stretchability) adhesive to skin, rubber, glass, and plastics, and could be repeatedly peeled-off and readhered to the skin. Moreover, the abundant quaternary ammonium (QA) groups in the zwitterionic moieties and the added QA groups endow it outstanding antibacterial properties (>99%). These stretchable tissue adhesive antibacterial hydrogels are promising for wound dressings and implantable devices.

Antifouling and antibacterial behavior of membranes containing quaternary ammonium and zwitterionic polymers

To overcome the organic-/bio- fouling of the membrane, a dual-functional ultrafiltration membrane containing quaternary ammonium and zwitterionic polymers via quaternization and surface radical polymerization was designed, and its antifouling and antibacterial behavior was studied. In this work, poly(vinylidene fluoride)/poly(methyl methacrylate-co-dimethylamino-2-ethyl methacrylate) (PVDF/P(MMA-co-DMAEMA)) blend membrane was quaternized by p-chloromethyl styrene (p-CMS), and the double bonds were introduced onto the membrane surface, which further participated in the polymerization of zwitterionic monomers on the membrane surface. The results indicated that the resultant membrane exhibited obviously improved hydrophilicity and weak positive charge (isoelectric point, 7.49). The membrane presented higher flux recovery ratio and lower protein adhesion compared with the pure PVDF membrane. Meanwhile, the membrane showed high-efficiency broad-spectrum antibacterial performance, that is, the bacteria killing efficiency of S. aureus and E. coli reached 98.2% and 97.0%, respectively. Moreover, the membrane effectively inhibited bacterial adhesion, which is important for the long-term antibacterial properties of membrane. This antifouling and antibacterial PVDF membrane may have potential in the long-term filtration process, especially when dealing with microbiologically contaminated water.

Open-to-Air RAFT Polymerization on a Surface under Ambient Conditions.

Oxygen (O2)-mediated controlled radical polymerization was performed on surfaces under ambient conditions, enabling on-surface polymer brush growth under open-to-air conditions at room temperature in the absence of metal components. Polymerization of zwitterionic monomers using this O2-mediated surface-initiated reversible addition fragmentation chain-transfer (O2-SI-RAFT) method yielded hydrophilic surfaces that exhibited anti-biofouling effects. O2-SI-RAFT polymerization can be performed on large surfaces under open-to-air conditions. Various monomers including (meth)acrylates and acrylamides were employed for O2-SI-RAFT polymerization; the method is thus versatile in terms of the polymers used for coating and functionalization. A wide range of hydrophilic and hydrophobic monomers can be employed. In addition, the end-group functionality of the polymer grown by O2-SI-RAFT polymerization allowed chain extension to form block copolymer brushes on a surface.

Fatigue-Resistant, Notch-Insensitive Zwitterionic Polymer Hydrogels with High Self-Healing Ability.

Introducing self-healing properties into hydrogels can prolong their application lifetime. However, achieving mechanical strength without sacrificing self-healing properties is still a major challenge. We prepared a series of zwitterionic polymer hydrogels by random copolymerization of zwitterionic ionic monomer (SBMA), cationic monomer (DAC) and hydrophilic monomer (HEMA). The ionic bonds and hydrogen bonds formed in the hydrogels can efficiently dissipate energy and rebuild the network. The resulting hydrogels show high mechanical strength (289-396 KPa of fracture stress, 433-864 % of fracture stress) and have great fatigue resistance. The hydrogel with a 1 : 1 molar ratio of SBMA:DAC possesses the best self-healing properties (self-healing efficiency up to 96.5 % at room temperature for 10 h). The self-healing process is completely spontaneous and does not require external factors to assist. In addition, the hydrogel also possesses notch insensitivity with a fracture energy of 12000 J m-2 . After combining the conductivity of RGO aerogel, the hydrogel/RGO composites show good strain sensitivity with high reliability and self-healing ability, which has certain significance in broadening the application of these zwitterionic hydrogels.

Non-amide based zwitterionic poly(sulfobetaine methacrylate)s as kinetic hydrate inhibitors

Applying kinetic hydrate inhibitors (KHIs) to avoid the pipeline blockage caused by hydrate formation in gas and oil industry is a comparatively effective and cost-saving method. The main ingredients in most KHIs are water-soluble polymers containing repeating amide group units, placed structurally close to hydrophobic groups. In this report we have synthesized a class of non-amide polymers, zwitterionic poly(sulfobetaine methacrylate)s, and investigated them as KHIs for the first time. Results show that the best zwitterionic polymers have good KHI efficacy with the key performance parameter being the length of the alkyl chain on the monomer unit side chains. Copolymer of the zwitterionic monomers and N-isopropylmethacrylamide (NIPMAM) gave much better increase in KHI performance with increasing concentration than the zwitterionic homopolymers. This result together with other related studies suggests that strong hydrogen-bonding groups like amide or amine oxide groups are important for high KHI performance. Reasons for this are discussed.

Effects of crosslink density in zwitterionic hydrogel coatings on their antifouling performance and susceptibility to silt uptake

Hydrogel coatings effectively reduce the attachment of proteins and organisms in laboratory assays, in particular when made from zwitterionic monomers. In field experiments with multiple species and non-living material, such coatings suffer from adsorption of particulate matter. In this study, the zwitterionic monomer 3-[N-(2-methacryloyloxyethyl)-N,N-dimethylammonio] propanesulfonate (SPE) was copolymerized with increasing amounts of the photo-crosslinker benzophenon-4-yloxyethyl methacrylate (BPEMA) to systematically alter the density of crosslinks between the polymer chains. The effect of increasing crosslink density on the antifouling (AF) performance of the coatings was investigated in laboratory assays and fields tests. In both cases, the AF performance was improved by increasing the crosslinker content. The coatings reduced protein, diatom, and barnacle accumulation, and showed better resistance to biomass accumulation. The findings underline that the marine AF performance of hydrogel coatings does not only depend on the specific chemical structure of the polymers, but also on their physico-chemical properties such as rigidity and swelling.

Innovative Skin Product Emulsions with Enhanced Antioxidant, Antimicrobial and UV Protection Properties Containing Nanoparticles of Pure and Modified Chitosan with Encapsulated Fresh Pomegranate Juice.

In the present study, a chitosan (CS) derivative with the 2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SDAEM) zwitterionic monomer was prepared through chemical modification. The successful synthesis of CS-SDAEM was confirmed by Fourier-transform Infrared (FTIR) and Nuclear Magnetic Resonance (1H-NMR) spectroscopies. Its crystallinity was studied by X-ray Diffraction (XRD), while in vitro cytotoxicity and cell viability assays established its biocompatibility. Filtered fresh pomegranate juice (PJ) was loaded in nanoparticles of neat CS and its derivative via ionic gelation method. Dynamic Light Scattering (DLS) revealed nanoparticles sizes varying between 426 nm and 4.5 μm, indicating a size-dependence on the polymer concentration used during encapsulation. High-performance liquid chromatography coupled with photodiode array and electrospray ionization mass spectrometry detection (LC-PDA-ESI/MS) revealed that PJ active compounds were successfully and in sufficient amounts encapsulated in the nanoparticles interior, whereas XRD indicated a crystalline structure alteration after nanoencapsulation. The resulted PJ-loaded nanoparticles were further utilized for the preparation of innovative O/W cosmetic emulsions. All produced emulsions exhibited good pH and viscosity stability for up to 90 days, while the sun protection factor (SPF) was enhanced due to the presence of the PJ. Enhanced antioxidant and antimicrobial properties due to the phenolic compounds of PJ were also observed.

Salt-responsive polyzwitterion brushes conjugated with silver nanoparticles: Preparation and dual antimicrobial/release properties

Attachment and colonization of bacteria on surfaces seriously impact human health as well as numerous technologies. In this contribution, a new zwitterionic monomer, 3-(dimethyl(4-vinylbenzyl)ammonio)butanesulfonate (DVBABS), was synthesized and a polymeric coating that not only kills bacteria but also releases them afterwards was constructed through rapid deposition of polydopamine (PDA) followed by in situ synthesis of Ag nanoparticles (NPs) and finally by grafting of polyDVBABS brushes using ARGET-ATRP (activators regenerated by electron transfer for atom transfer radical polymerization). The PDA catechol groups immobilized the Ag NPs, which were responsible for the inhibition of bacterial growth, and a change from water to salt solution effected a reversible conformational transition of the polyzwitterion, which was responsible for bacterial release. For both Escherichia coli (E. coli) and Staphylococcus (S. aureus), the dual-function coating can kill ≥99% of attached bacteria and then rapidly release ≥95% of all attached bacteria. Both functions were well retained over several cycles of killing and release. Based on the substrate-independent adhesion of PDA coatings, exemplified here for titanium, cotton textile, polypropylene and polydimethylsiloxane surfaces, a broad spectrum of applications are envisaged.

Integration of photo-induced biocidal and hydrophilic antifouling functions on nanofibrous membranes with demonstrated reduction of biofilm formation

Survival and pathogenic microbial adhesions on surfaces of materials followed by the formation of biofilms with robust resistance to antibiotics constitute the forefront of disease transmissions. Conventional strategies responding to this challenge are rather limited due to the biofouling effect of microorganisms or the irreversible consumption of antimicrobial agents embedded into the materials. Herein, we report an approach of combining photo-induced rechargeable biocidal properties with microbial resisting and releasing zwitterionic hydrophilic functions on surfaces of materials to improve antifouling performances. Poly(vinyl alcohol-co-ethylene) (EVOH) nanofibrous membranes (NFMs) were chemically incorporated with both 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BPTCD), a photoactive chemical, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), a zwitterionic monomer. Both functional agents work independently and construct concerted microbial resisting, killing, and releasing functions to reduce microbial contamination and biofilm formation. The resulted SBMA@EVOH NFMs exhibited integrated features of large ROS production capacity, ease of photoactive rechargeability and controllability, long-term stability, high biocidal efficacy (>99.9999% via contact killing), and promising antifouling performance, which enable the SBMA@EVOH NFMs to serve as a biocidal material for food safety and medical applications.

Micro- and macroscopically structured zwitterionic polymers with ultralow fouling property

HypothesisPolyzwitterions as a promising class of materials are often used to construct antifouling surfaces with optimized conformation and compositions for a wide variety of antifouling applications. While numerous zwitterionic polymers have been identified for their antifouling capacity, the exact relationship among molecular structure, surface hydration property, and antifouling performance of zwitterionic polymers at different scales still remains elusive. Experimentswe first designed and synthesized a new zwitterionic monomer of 3-(4-(methacryloyloxy)-1-methylpiperidin-1-ium-1-yl)-propane-1-sulfonate (MAMPS), then used MAMPS monomers to fabricate into homogenous polymer brushes on Au substrate using SI-ATRP and heterogeneous double-network (DN) hydrogels combining with Agar network via one-pot, heating-cooling-photopolymerization method, and finally evaluated their antifouling ability to resist the adsorption of protein/cell/bacteria on the two different polymer forms at microscopic and macroscopic scales. FindingsFor microscopic polyMAMPS brushes, they exhibited excellent resistance to nonspecific protein adsorption from both undiluted blood serum/plasma (0.3–5 ng/cm2), cell adhesion up to 3 days, and clinically relevant bacterial attachment for 72 h at the optimal film thicknesses of 20–40 nm. For macroscopic Agar/polyMAMPS DN hydrogels, they also exhibited approximately 96% less protein adhesion than tissue culture polystyrene (TCPS). Different structured materials consisting of polyMAMPS at both micro- and macro-scales demonstrate its excellent, intrinsic antifouling property, which could be related to their highly water binding character of zwitterionic groups. PolyMAMPS materials, alternative to commonly used poly(sulfobetaine methacrylate) (polySBMA) and poly(carboxybetaine methacrylate) (polyCBMA) zwitterions, hold great promise for antifouling designs and applications.

RAFT polymerization of tertiary sulfonium zwitterionic monomer in aqueous media for synthesis of protein stabilizing double hydrophilic block copolymers

AbstractThe reversible addition‐fragmentation chain‐transfer (RAFT) polymerization of a tertiary sulfonium‐containing zwitterionic monomer (N‐acryloyl‐L‐methionine methyl sulfonium salt: A‐Met[S+]‐OH) was performed in aqueous media in the presence of a water‐soluble chain‐transfer agent (CTA). Several parameters, such as the radical initiator, nature of the salt used as an additive, polymerization temperature, and solvent (water, buffer solution, and mixed solvents), were studied. The polymerization of A‐Met(S+)‐OH in acetate buffer using a trithiocarbonate‐type CTA having two carboxylic acid moieties proceeded in a controlled fashion at 45°C, as confirmed by the low polydispersity of the products (M w/M n < 1.1) and pre‐determined molecular weights. Poly(ethylene glycol)‐based macro‐CTA was also employed for the polymerization of A‐Met(S+)‐OH in mixed solvents (H2O/EtOH and H2O/DMF = 70/30 vol%) to afford novel nonionic‐zwitterionic double hydrophilic block copolymers. The chain extension of the hydrophilic poly(N,N‐dimethylacrylamide) macro‐CTA with A‐Met(S+)‐OH was well controlled in pure water under the appropriate conditions, resulting in the formation of block copolymers with “as‐designed” chain structures and relatively low dispersities (M w/M n < 1.3). The resulting sulfonium‐containing double hydrophilic block copolymers having optimal nonionic/zwitterionic balance were efficient protein‐stabilizing agents.

Synthesis and properties of a betaine type copolymer filtrate reducer

With the exploitation of ultra-high temperature deep wells, the fluid loss reducer as the core treatment agent of drilling fluid, in addition to ensuring the fluid loss performance, it needs to have both high temperature and high salt resistance and certain inhibition. Thus, N-(3-dimethylallyl)methacrylamide and 1,3-propane sultone were used to synthesize a betaine-type zwitterionic functional monomer named DMAPMAS. A zwitterionic copolymer PADAN as a fluid loss reducer for drilling fluids was prepared by attaching 2-acrylamide-2-methylpropanesulfonic acid, N-vinylpyrrolidone and synthetic DMAPMAS to the main chain of acrylamide via aqueous solution free radical polymerization. It not only has great thermal but has good fluid loss and inhibition performance. In addition, the addition of PADAN can effectively improve the particle size distribution of the drilling fluid system. The combination of PADAN and sulfonated polymer SMC, SMP-II and SPNH has the effect of reducing the fluid loss of drilling fluid. Moreover, it has good adaptability to a variety of drilling fluid systems. Applied to the sulfonation drilling fluid system and the polysulfide KCl drilling fluid system, it has the significant effect in fluid loss reduction and less impact on the rheological properties to adapt to various drilling fluid systems.

High strength zwitterionic nano-micelle hydrogels with superior self-healing, adhesive and ion conductive properties

Zwitterionic nano-micelle hydrogels were prepared by in situ co-polymerization of zwitterionic monomer- [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) and nonionic monomer-hydroxyethyl methacrylate (HEMA) for the first time using Pluronic F127 di-acrylate (F127DA) as macro-crosslinkers. This novel hydrogel featured tough mechanical properties (sustained a strain at 98% without fracture, and a tensile fracture strain at about 1000%), adhesiveness, as well as good conductive properties (two times than the traditional chemical cross-linked zwitterionic hydrogels). Due to strong electrostatic attraction constructed by the positively and negatively charged groups in the zwitterionic hydrogels, and the reversible dissociation-association of the micelle cross-linked zones via hydrophobic associations in the gel network, the prepared micelle-based hydrogels also exhibited excellent self-healable properties, the self-healed hydrogels exhibited almost the same stretching behavior compared with the original hydrogels. This superior zwitterionic nano-micelle hydrogel could therefore have great potential in applications like wearable sensors, human-health monitors, artificial skin and axon.

In situ synthesis of amply antimicrobial silver nanoparticle (AgNP) by polyzwitterionic copolymers bearing hydroxyl groups

Zwitterionic monomer methyacryloxyethyl sulfobetaine (MAES) copolymerized with hydroxyethyl methacrylate (HEMA) forming random copolymer with some block characteristics in a controlled manner. The polyzwitterionic copolymer P(MAESx-ran-HEMAy) (PMxHy, where x and y were the degrees of polymerization of MAES and HEMA, respectively), which bearing hydroxyl groups that served as both reducing and capping reagent for in situ AgNPs synthesis without exogenous additions. The in situ formed uniform AgNPs composites adopted a typical “core-shell” structure where AgNPs served as cores, and PMH were shells. The stability of the AgNPs composites was promoted by chelation of AgNPs core and the generated aldehyde on PMH during silver ions (Ag+ ions) reduction. Size of the AgNPs composites directly correlated with [MAES] to [HEMA] ratio in PMH and the highest yield of AgNPs composites was achieved when PM20H27 to AgNO3 weight ratio equaled 30%. The AgNPs composites originating from PM50H26 showed the most potent bactericidal activity through the membrane perturbation mechanism. Besides, the AgNPs composites confirmed safe for mammalian cells by hemolysis and cytotoxicity tests.

Photocross-linking Kinetics Study of Benzophenone Containing Zwitterionic Copolymers.

The kinetics of benzophenone (BP) and its derivatives have been widely studied in different solvents by nanosecond laser flash photolysis as well as in the polymer matrix. With the development of functional polymer coating, BP, as well as other photocross-linkers, has been incorporated into the polymer backbone or side chain to form the covalent connection between polymer coatings and substrates, which can improve the mechanical and chemical stability of the coatings. In this work, a series of BP pendent zwitterionic copolymer kinetics were investigated using UV–vis for the first time. Because of the high hydrophilicity of the zwitterionic monomer, the influence of the polymer matrix’s polarity on the cross-linking rate was observed. With a higher zwitterionic percentage in the copolymer, the polarity of the copolymer increases, BP reactivity decreases, and a hypothesis between the BP rate constant and partial coefficient log P was raised. Moreover, the thermal property is also an important factor affecting the BP reactivity. For polymers with high glass-transition temperature, the reactivity was not dominated by the chemical environment such as polarity, and the restricted segment movement reduces the cross-linking rate. Additionally, the ring substituents show similar effects to BP pendent copolymers as with small molecules. Electron-withdrawing groups help to stabilize the BP triplet radical and facilitate cross-linking, while electron-donating groups work conversely. Therefore, polarity, thermal properties, and substituents should be taken into consideration when designing BP-containing functional polymers.

Zwitterionic Polysulfamide Drug Nanogels with Microwave Augmented Tumor Accumulation and On‐Demand Drug Release for Enhanced Cancer Therapy

AbstractZwitterionic polymers demonstrate as a class of antifouling materials with long blood circulation in living subjects. Despite extensive research on their antifouling abilities, the responsive zwitterionic polymers that can change their properties by mild outside signals are poorly explored. Herein, a sulfamide‐based zwitterionic monomer is developed and used to synthesize a series of polysulfamide‐based (poly (2‐((2‐(methacryloyloxy)ethyl) dimethylammonio)acetyl) (phenylsulfonyl) amide (PMEDAPA)) nanogels as drug carriers for effective cancer therapy. PMEDAPA nanogels are proved to exhibit prolonged blood circulation without inducing the accelerated blood clearance phenomenon. Intriguingly, PMEDAPA nanogels can sensitively respond to hyperthermia by adjusting the crosslinker degree. After modified with transferrin (Tf), the nanogels (PMEDAPA‐Tf) achieve shielded tumor targeting at normothermia, while exhibiting recovered tumor targeting at hyperthermia, leading to enhanced tumor accumulation. Meanwhile, PMEDAPA‐Tf nanogels show superior penetration ability in 3D tumor spheroids and faster drug release at hyperthermia compared with that at normothermia. In combination with mild microwave heating (≈41 °C), the drug‐loaded PMEDAPA‐Tf nanogels show a pronounced tumor inhibition effect in a humanized orthotropic liver cancer model. Therefore, the study provides a novel hyperthermia‐responsive zwitterionic nanogel that can achieve augmented tumor accumulation and on‐demand drug release assisted with clinically used microwave heating for cancer therapy.

DFT zwitterion model for vibrational and electronic structure of unnatural 3-amino-3-(4-fluorophenyl)propionic acid, aided by IR and Raman spectroscopy

3-Amino-3-(4-fluorophenyl)propionic acid - a fluorinated building block in synthesis and a non-proteinogenic amino acid - belongs to the class of β-amino acids. We present here ab initio and DFT computed zwitterionic (ZW) monomer and dimer structures of 3-Amino-3-(4-fluorophenyl)propionic acid. These structures comprise intra- and inter-H-bonds (dimer), namely, N–H⋯O bonds formed between NH3+ and COO¯ moieties and the inter-N−H⋯O bond vibrational modes are correlated to the characteristic absorptions in the experimental IR spectrum. We propose two structures for 3-Amino-3-(4-fluorophenyl)propionic acid: a ZW monomer resulting from the explicit solvation model with four water molecules and a ZW dimer resulting from the implicit solvation model in water. By varying the bond length, rH … O around 1.70 Å, we get stable degenerate structures, getting the most stable ZW dimer mentioned above at 1.72 Å. Computed vibrational frequencies of NH3+ and COO¯ moieties for the ZW cluster and dimer complement each other in so far as good agreement with experimental IR and Raman spectra. We also have characterized both H-bonds using electronic properties computed from NBO, AIM and NCI methods. The natural bond analysis has shown that in both intra- and inter- N–H⋯O bonding, there is delocalization of electronic charge from n orbital on the O atom to σ∗ orbital on the N atom. The bond critical points are present between the cationic NH3+ and anionic COO¯ moieties along with atomic bond path confirming the N–H⋯O bond and is shown to be medium strong by NCI.

Simultaneous amphiphilic polymer synthesis and membrane functionalization for oil/water separation

This work scrutinizes a versatile process during which amphiphilic copolymers (made of styrene and sulfobetaine methacrylate, ethylene glycol methacrylate or vinylpyrrolidone) are simultaneously copolymerized and coated on microporous poly (vinylidene fluoride) (PVDF) membranes. Changing the nature of the hydrophilic monomer and the reaction conditions, it is possible to regulate the wetting properties of the membranes by water and oil. The main surface physical properties of the membranes were not modified for a reaction/deposition bath containing up to 50% styrene monomer, but larger styrene amounts led to aggregate formation. A 50% molar ratio in hydrophobic/hydrophilic unit led to a suitable balance between stability and hydration, resulting in optimized water permeation and oil repellence. Gravity-driven separation of oily wastewaters was doable with all selected membranes (St50S50, St50P50 and St50V50) and oils tested (toluene, hexane, diesel). Nevertheless, it is highlighted that PEGylated surfaces offer the best overall compromise between separation kinetic and separation efficiency. Results also suggested that zwitterionization with larger amounts of zwitterionic monomers is not practical, possibly because it leads to a hydration layer too tight, which slows down the gravity-driven separation. This study demonstrates the effectiveness/versatility of this surface modification method to quickly hydrophilize PVDF membranes applied to energy-efficient separation of emulsions.

Activation and stabilization of lipase by grafting copolymer of hydrophobic and zwitterionic monomers onto the enzyme

We report herein new enzyme-polymer conjugates synthesized by grafting polymerization onto Candida rugosa lipase (CRL) with zwitterionic carboxyl betaine methacrylate (CBMA), hydrophobic tert-butyl methacrylate (TBMA) and their equimolar mixture, which respectively created CRL-pCBMA, CRL-pTBMA, and CRL-p(T50-C50). All the enzyme conjugates presented improved catalytic activity, thermostability and pH tolerance, and the kinetic studies indicated that the polymer-grafting resulted in significantly higher enzymatic reaction efficiency and enzyme-substrate affinity. CRL-pTBMA increased the catalytic activity by 2.26-fold and half-life by 43.1-fold at 50 °C as compared with the free enzyme due to the interfacial activation effect of TBMA. However, despite the lower activity of the copolymer conjugate (1.56 times of free enzyme), CRL-p(T50-C50), its half-life was 2.2-fold higher than CRL-pTBMA. This was due to the stabilization effect of the zwitterionic monomer component (CBMA) in the copolymer. This is evident from the similar stability of CRL-p(T50-C50) with CRL-pCBMA, but the latter showed lower activity than the former due to the lack of the interfacial activation effect of TBMA. Thus, a zwitterionic/hydrophobic balance is of vital importance to enhance the enzymatic performance. Spectroscopic characterizations revealed the changes in the microenvironment and secondary structures of the enzyme in CRL-polymer conjugates. Therefore, modification with zwitterionic-hydrophobic copolymer was found more effective in improving the catalytic performance of lipase.