Facile surface modification of PVDF microfiltration membrane by strong physical adsorption of amphiphilic copolymers

To endow the surface of poly(vinylidene fluoride) (PVDF) microfiltration (MF) membranes with hydrophilicity and antifouling property, physical adsorption of amphiphilic random copolymers of poly(ethylene glycol) methacrylate (PEGMA) and poly(methyl methacrylate) (PMMA) (P(PEGMA‐r‐MMA)) onto the PVDF membrane was performed. Scanning electron microscopy (SEM) images showed that the adsorption process had no influence on the membrane structure. Operation parameters including adsorption time, polymer concentration, and composition were explored in detail through X‐ray photoelectron spectroscopy (XPS), static water contact angle (CA), and water flux measurements. The results demonstrated that P(PEGMA‐r‐MMA) copolymers adsorbed successfully onto the membrane surface, and hydrophilicity of the PVDF MF membrane was greatly enhanced. The antifouling performance and adsorption stability were also characterized, respectively. It was notable that PVDF MF membranes modified by facile physical adsorption of P(PEGMA₅₈‐r‐MMA₃₃) even showed higher water flux and better antifouling property than the commercial hydrophilic PVDF MF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3112–3121, 2013     

Preparation,surface wetting properties,and protein adsorption resistance of well‐defined amphiphilic fluorinated diblock copolymers

Novel well‐defined amphiphilic fluorinated diblock copolymers P(PEGMA‐co‐MMA)‐b‐PC₆SMA were synthesized successfully by RAFT polymerization and characterized by FTIR, ¹HNMR and GPC. For copolymer coatings, static contact angles, θ, with water (θ_water ≥ 109.5^°) and n‐hexadecane (θ_hexadecane ≥ 68.9^°) pointed to the simultaneous hydrophobic and lipophobic characteristics of the copolymer surfaces. Dynamic contact angle measurements indirectly demonstrated that copolymer films underwent surface reconstruction upon contact with water, which results in a surface with surface coverage of polar PEG units. Moreover, the distinct nanoscale microphase segregation structures were proved by atomic force microscopy (AFM) images. Finally, using bovine serum albumin (BSA–FITC) as the model protein, copolymers exhibited excellent protein adsorption resistance. It is believed that the combination of surface reorganization and nanometer‐scale microphase segregation structure endows the excellent protein resistance for amphiphilic fluorinated copolymers. These results provide deeper insight of the effect of surface reconstruction and microphase segregation on the protein adsorption behaviors, and these amphiphilic fluoropolymers can expect to have potential applications as antifouling coatings in the field of marine and biomedical. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41167.     

A novel mono‐methacryloyloxy terminated fluorinated macromonomer used for the modification of UV curable acrylic copolymers

A novel macromonomer containing fluorinated units (PHFBMA‐GMA) was synthesized through a two‐step procedure: firstly, hexafluoro‐butyl methacrylate (HFBMA) was polymerized in the presence of functional chain transfer agent 3‐mercaptopropionic acid (MPA) and then the carboxyl acid group terminated polymer was end‐capped with glycidyl methacrylate (GMA). Chemical structures of PHFBMA‐GMA were characterized by gel permeation chromatography, fourier transform infrared spectroscopy (FTIR), and ¹H nuclear magnetic resonance (NMR). Subsequently, PHFBMA‐GMA was employed as reactive surface additives added into UV‐cured polyacrylate to modify UV‐curable coatings. It is convenient to control the tail length of the fluorinated segments in this study by adjusting the ratio of initiator and chain transfer agent. The influence of both the concentration and the molecular weight of PHFBMA‐GMA on the surface properties of UV‐cured films was investigated. With increasing both the concentration and the molecular weight of PHFBMA‐GMA, the surface energy of the UV‐cured films decreased. X‐ray photoelectron spectroscopy was employed to characterize and quantify the surface composition and the results confirm the enrichment of fluorinate atoms on the surface. Moreover, the physical properties of UV‐cured films, such as gel content, water absorption, pencil hardness, adhesion, chemical resistance, mechanical properties, optical transmittance, and thermal properties, were also investigated in detail. The novel macromonomer was economical but effective to modify the properties of the UV‐curable coatings. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43116.     

Synthesis and properties of gradient copolymers of butyl methacrylate and fluorinated acrylate via RAFT miniemulsion copolymerizations

A series of gradient fluorinated copolymers with a broad variation of the monomer units in the polymer chain were synthesized via semibatch CPDB‐mediated RAFT miniemulsion polymerization technique. In the presence of RAFT agent 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB), the copolymerization of BMA and FMA in miniemulsion exhibited typical features of a controlled molecular weights and narrow polydispersities. The macromolecular structure and thermal behavior of the synthesized fluorinated copolymers were investigated in detail. The DSC analyses show that the gradient copolymers showed a unique thermal behavior with broad range of transition temperature. It was also confirmed that the fluorinated gradient copolymer exhibited obvious surface segregation structure and ultra‐low surface energy between 16.8 and 20.3 mN/m. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42936.     

Synthesis and characterization of hydroxypropyl terminated polydimethylsiloxane‐polyurethane copolymers

Polyurethane (PU) block copolymers were synthesized using prepared hydroxypropyl terminated polydimethylsiloxane (HTPDMS MW 990) and polyether diols (N‐210) as soft segment with 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol. This low molecular weight polydimethylsiloxanes (PDMS) containing hydroxypropyl end‐groups displayed better compatibility with PU than common PDMS. In this article, we illustrate its synthesis routes and confirmed the proposed molecular structures using NMR and infrared radiation (IR). We varied the contents of HTPDMS and N‐210 in soft segments (HTPDMS—N‐210: 0 : 100, 20 : 80, 40 : 60, 60 : 40, 80 : 20, and 100 : 0) to synthesize a series of PDMS‐PU copolymer. IR spectroscopy showed the assignment characteristic groups of each peak in copolymers and confirmed that the desired HTPDMS‐PU copolymers have been prepared. The different thermal, dynamic mechanical and surface properties of the copolymers were compared by thermogravimetry, DMA, contact angle and solvent resistance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and rheological behavior of hydrophobically modified block copolymers

Hydrophobically modified polymers were synthesized via esterification reactions between a commercial triblock copolymer composed of ethylene oxide (EO) and propylene oxide (PO) segments (EO₂₀PO₇₀EO₂₀) and lauric and oleic acids. Rheological studies of aqueous systems containing the original copolymer and the synthesized products were performed to evaluate the effects of chemical modification, the presence of salt, and temperature on the rheology of the systems due to changes in the micellar structures. It was verified that the systems containing the synthesized products presented shear‐thinning behavior even in the absence of salt. In addition, increasing the temperature and salt concentration enhanced the hydrophobic character of the poly(propylene oxide) segment and reduced the hydration of the poly(ethylene oxide) segment; this favored the adequate packing needed to form long, wormlike micelles and resulted in pronounced shear thinning. The formation of a complex micelle structure probably occurred in the systems above the critical micellar temperature of the original copolymer because under this condition the molecules presented three alternate hydrophobic segments that had to dive into the micelle structure. The formation of long, wormlike micelles was also evidenced by the Maxwellian behavior observed in rheological oscillatory measurements. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of well‐defined glycoconjugate polyacrylamides via preactivated polymers prepared by ATRP

Poly(N‐acryloxysuccinimide) (polyNAS) with narrow molecular weight distributions (MWD) applicable for the preparation of well‐defined glycoconjugate polyacrylamides were successfully prepared by atom transfer radical polymerization (ATRP). The structures of polyNAS were characterized by ¹H‐NMR and GPC. GPC results showed that the molecular weight polydispersity indices (PDI) range from 1.17 to 1.29. The molecular weights could be calculated based on ¹H‐NMR results but GPC results of polyNAS by using 0.01M LiBr/DMF did not give accurate molecular weights, probably because of the complex interaction in the system. The effects of free N‐hydroxysuccimide produced in the polymerization processes on the free‐radical concentrations and apparent initiation efficiencies of ATRP were discussed. Well‐defined glycoconjugate polyacrylamides (i.e., with narrow molecular weight distributions and designed glycoconjugate degrees) were prepared by substituting N‐oxysuccimide units with galactosamine followed by reaction of ethanolamine. The galactose conjugate degrees were determined by ¹H‐NMR and the total substitutions of N‐oxysuccimides were verified by ¹H‐NMR and FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 189–194, 2005     

Octadecyl‐silica—PVDF membrane of superior MD desalination performance

Despite its widespread industrial and residential uses for production of potable water, the reverse osmosis (RO) desalination process has some drawbacks by discharging harmful concentrated saline water as reject stream. A hydrophobic porous membrane can treat such environmentally unfriendly RO reject stream via Membrane Distillation (MD) process. Here, we describe preparation of superior polyvinylidenefluoride (PVDF) membrane modified with superhydrophobic silica nanoparticles for desalination application. Superhydrophobicity (contact angle of 151°) of silica nanoparticles of 7 nm sizes was achieved by reaction of the silica particles with octadecyltrichlorosilane in toluene to form ? Si? O? Si? links with C18 alkyl chain. A homogeneous polymer dope mixture containing a desired amount of modified silica colloids suspended in toluene was used for the membrane preparation. The PVDF membrane with optimal silica content exhibited excellent flux with >99% salt rejection efficiency when used for MD at room temperature from the saline water feed of 3.5 wt % NaCl. The prepared hydrophobic PVDF membrane has the potential for MD application in treating the RO reject stream and other aqueous industrial effluents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46043.     

Jamming rheology of model cementitious suspensions composed of comb‐polymer stabilized magnesium oxide particles

The colloidal microstructure of concentrated suspensions containing anionic comb‐polymer‐stabilized magnesium oxide (MgO) particles in water was analyzed by shear rheometry for indications of changes in particle microstructure based on particle size and comb‐polymer usage. As the suspensions were sheared at different rates, jamming in the sheared MgO suspensions was observed as shear stress overshoots. The shear‐induced evolution of the suspension's microstructure was strongly related to the perceived interactions between neighboring MgO particles in the suspension. In the jammed state, interactions are believed to be enhanced by the formation of entanglements between opposing comb‐polymer side‐chains. Steric repulsion between side‐chains was lessened for large particles on account of their diameters, which further enabled side‐chain entanglement during close particle contact under shear. Suspensions with relatively wide particle size distributions (0.5–400 μm) were theorized to form hydrocluster aggregates, while suspensions with narrower particle size distributions (0.5–40 μm) most likely resulted in networked microstructures under the influence of the chain entanglements from the adsorbed comb‐polymer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40429.     

Modification of surface properties of wool fabric with linde type a nano‐zeolite

Wool is a naturally occurring composite fiber consisting of keratin and keratin‐associated proteins as the key molecular components. The outermost surface of wool comprises a lipid layer that renders the surface hydrophobic, which hinders certain fabric processing steps and moisture management properties of wool fabrics. In this study, Linde Type A (LTA) nano‐zeolite (a Na⁺‐, Ca²⁺‐, and K⁺‐exchanged type A zeolite) was integrated onto the surface of wool using 3‐mercaptopropyl trimethoxy silane as a bridging agent. The resultant surface morphology, hydrophilicity, and mechanical performance of the treated wool fabrics were evaluated. Notably, the surface hydrophilicity of wool increased dramatically. When wool was treated with a dispersion of 1 wt % zeolite and 0.2 wt % silane, the water contact angle decreased from an average value of 148° to 50° over a period of approximately 5 min. Scanning electron microscopic imaging indicated good coverage of the wool surface with zeolite particles, and infrared spectroscopic evaluation demonstrated strong bonding of the zeolite to wool keratins. The zeolite application showed no adverse effects on the tensile and other mechanical properties of the fabric. This study indicates that zeolite‐based treatment is potentially an efficient approach to increasing the surface hydrophilicity and modifying other key surface properties such as softness of wool and wool fabrics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42392.     

Synthesis and characterizations of hydrophobically associating water‐soluble polymer with nonionic surfmer

In this article, a hydrophobically associating copolymer (2‐acrylamido)‐2‐methylpropanesulfonic acid (AMPS)/AA‐EO₂₅C₁₂ was synthesized by AMPS and nonionic surfmer AA‐EO₂₅C₁₂ through free radical copolymerization. The structure of copolymer was characterized by FT‐IR and ¹H‐NMR. The properties of copolymer were studied and the results indicated that the copolymer exhibits good thickening ability due to intermolecular hydrophobic associations as the apparent viscosity of the copolymer solution increases sharply with increasing polymer concentration. Compared with homopolymer PAMPS, the rheological test indicates that the copolymer solution shows shear thickening behavior at low shear rate region. Besides, the copolymer exhibits interfacial activity as it can reduce the interfacial tension to 10° level, and ability to form emulsion with good stability, which is due to successfully introducing the structure of nonionic surfmer AA‐EO₂₅C₁₂ to the polymer chain. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43195.     

Synthesis of cyclohexanone formaldehyde resin‐methylmethacrylate block‐graft copolymers via ATRP

Well defined block‐graft copolymers of cyclohexanone‐formaldehyde resin (CFR) and methylmethacrylate (MMA) were prepared via atom transfer radical polymerization (ATRP). In the first step, cyclohexanone formaldehyde resin (CFR) containing hydroxyl groups were modified with 2‐bromopropionyl bromide. Resulting multifunctional macroinitiator was used in the ATRP of MMA using copper bromide (CuBr) and N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) as catalyst system at 90°C. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (¹H‐NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and molecular weight measurement. Molecular weight distributions of the CFR graft copolymers were measured by gel permeation chromatography (GPC). M_n values up to 19,000 associated with narrow molecular weight distributions (polydispersity index (PDI) < 1.6) were obtained with conversions up to 49%. Coating properties of synthesized graft copolymers such as adhesion and gloss values were measured. They exhibited good adhesion properties on Plexiglas substrate. The thermal behaviors of all polymers were conducted using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Long‐term stable hydrophilic surface modification of poly(ether ether ketone) via the multilayered chemical grafting method

The aging phenomena of a poly(ether ether keton) (PEEK) surface hydrophilically modified via various protocols was investigated. The use of plasma treatment or chemical etching methods offers a relatively convenient surface modification route. However, the effects of hydrophilic treatment quickly disappeared and its original surface property was recovered within a few hours or a few days when stored at ambient conditions. Surface treatment based on a single‐layered chemical grafting method rendered an excellent hydrophilic surface with an initial contact angle of <15° and an improved retardation of surface aging. However, the contact angle of the modified PEEK specimen gradually increased with time and eventually reached ～50° after 23 days. A new method for the long‐term stable hydrophilic surface treatment of PEEK using a multilayered chemical grafting strategy was also developed. With this regard, aging of the modified surface could be significantly retarded over ～90 days. It was believed that the effectiveness of the surface modification and the retarded aging phenomena via the multilayered hydrophilic treatment could be attributed to mechanical and chemical stability of the covalently bonded active surface groups on the grafted polymer networks. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46042.     

Crystallization behavior of poly(ethylene terephthalate‐co‐neopentyl terephthalate‐co‐ethylene isophthalate‐co‐neopentyl isophthalate) copolyester and its application in laminated tin‐free steel

A low crystallinity, the copolyester poly(ethylene terephthalate‐co‐neopentyl terephthalate‐co‐ethylene isophthalate‐co‐neopentyl isophthalate) (PENIT) was synthesized and applied for laminated tin‐free steel. The structures and thermal properties of the copolyester were characterized by ¹H‐NMR, thermogravimetry analysis, differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscopy. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscopy results show that the crystallization ability of the copolyester decreased obviously. Meanwhile, the peel strength, crystallinity, and water‐vapor permeability of the copolyester film were also measured at varied lamination temperatures. The result confirm that an improvement in the lamination temperature led to an increased ratio of amorphous PENIT to crystalline PENIT and decreased structural orientation, and the decrease in the structural orientation sped up the increase in the rate of water‐vapor permeability. On the basis of the purpose of reducing a detrimental effect on the corrosion resistance caused by water permeation, a reasonable lamination temperature was selected. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42308.     

Flow‐induced solidification of high‐impact polypropylene copolymer compositions: Morphological and mechanical effects

Polypropylene‐based impact copolymers are a complex composition of matrix material, a dispersed phase and many optional modifiers. The final heterophasic morphology of such systems is influenced significantly by the processing step, adding an additional level of complexity to understanding the structure‐property relation. This topic has hardly been studied so far. The effect of thermal history and shear flow on the solidification process of three different compositions of a polypropylene‐based impact copolymer, i.e., one base material and two compounds with either high density polyethylene or ethylene‐co‐octene added, is investigated. Samples are examined using differential scanning calorimetry, extended dilatometry, transmissions electron microscopy, and finally, tensile testing. With flow, the materials show pronounced flow‐enhanced crystallization of the matrix material and deformed filler content. Compared to the base polymer, the stress–strain response of the compounded samples shows a lower yield stress and more pronounced influence of shear, reflected in the increasing strain hardening modulus. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42040.     

Synthesis and characterization of amphiphilic PMTFPS‐b‐PEO diblock copolymers

A series of new amphiphilic poly[methyl(3,3,3‐trifluoropropyl) siloxane]‐b‐poly(ethyleneoxide) (PMTFPS‐b‐PEO) diblock copolymers with different ratio of hydrophobic segment to hydrophilic segment were prepared by coupling reactions of end‐functional PMTFPS and PEO homopolymers. PMTFPS‐b‐PEO diblock copolymers synthesized were shown to be well defined and narrow molecular weight distributed by characterizations such as NMR, GPC, and FTIR. Additionally, the solution properties of these diblock copolymers were investigated using tensiometry and transmission electron microscopy. Interestingly, the critical micellization concentration increases with increasing length of hydrophobic chain. Transmission electron microscopy studies showed that PMTFPS‐b‐PEO diblock copolymers in water preferentially aggregated into vesicles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Gamma‐irradiated metallocenic polyethylene and ethylene‐1‐hexene copolymers

The aim of this work is to present a detailed study of the changes introduced by gamma radiation on several metallocenic polyethylene copolymers. Therefore, metallocenic polyethylene and copolymers with 3.3, 9.2, and 16.1 mol % of hexene comonomer content were synthesized and irradiated with ⁶⁰Co gamma radiation under vacuum at room temperature with radiation doses ranging from 0 to 100 kGy. Size Exclusion Chromatography data show that crosslinking reactions predominate over scission, even for the copolymer with the highest tertiary carbon content. Over a certain critical dose, which depends on the molecular weight and molecular structure of the initial polymer, an insoluble gel forms. The irradiated polymers also exhibit complex rheological behavior with increasing melt viscosity and elasticity, consistent with long chain branching and/or crosslinking. FTIR confirms depletion of terminal vinyl groups and increase of trans unsaturations with dose. The rate at which these two reactions evolve seems to depend on the comonomer content of the irradiated copolymers. Differential scanning calorimetry and Raman spectroscopy analyzes indicate less crystallinity and thicker interphases in irradiated materials. A mathematical model, which accounts for scission and crosslinking reactions, fitted well the evolution with radiation dose of the measured molecular weight data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Self‐assembling amphiphilic PEGylated block copolymers obtained through RAFT polymerization for drug‐delivery applications

In this work, ring‐opening polymerization and reversible addition‐fragmentation chain transfer polymerization (RAFT) have been employed for the production of block copolymers where the backbone is brushed with poly(ethylene glycol) (PEG) and polyester chains. Because of their amphiphilic properties, they are able to self‐assemble in water, forming micelles. Molecular dynamics simulations have been accomplished to study the behavior of the copolymer single chain in water, and the self‐assembly properties have been characterized and correlated to the copolymer structure in terms of critical micellar concentration and particle size. As a proof of their flexibility, these materials have been employed for the production of polymer–lipid hybrid nanoparticles with tunable dimensions (from 120 to 260 nm) adopted for the controlled release of anticancer compounds (paclitaxel and curcumin). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43084.     

Synthesis and characterization of PS‐b‐PDMS‐b‐PS triblock copolymer

A series of polystyrene‐b‐poly(dimethylsiloxane)‐b‐polystyrene (PS/PDMS/PS) triblock copolymers had been synthesized by atom transfer radical polymerization (ATRP). The products had been characterized by Fourier transform infrared, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, contact angle, and scanning electron microscope. The results indicate that the PS chains have been successfully blocked onto the PDMS back bone, and the PS‐b‐PDMS‐b‐PS triblock copolymers have low‐surface tension, good thermal stability, and microphase separation configuration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Control of well‐defined crater structures on the surface of biaxially oriented polypropylene film by adding nucleators

While it is common to add anti‐blocking agents to biaxially oriented polypropylene (BOPP) films for general use in order to prevent blocking against each other, the technology of crater‐like film surface roughness formed on the BOPP films without any additives is well known in the industrial BOPP film areas. Numerous studies have been reported on the crater‐like film surface roughness on the BOPP films since the 1980s, but its formation mechanism and the controlling method of the crater‐like film surface roughness are yet to be clarified. In our previous reports, we presented a new hypothesis of crater formation mechanism from a new point of view on sheet morphology and crater shape on the BOPP film surface. It was strongly influenced by the crystal grain shape in the surface layer of PP sheet. In this report, it was clarified that a nucleator has a big influence on the formation of the crystal grains in the surface layer of PP sheets and on the formation of craters. In addition, craters did not form on the BOPP films stretched from the sheet of which the skin layer with crystal grain was shaved, even though β crystal still remained. It was clarified that the crystal grain is trans‐crystal from the observation using TEM. Therefore, it is concluded that the existence of β crystals in the surface layer of PP sheets is not essential in order to produce craters on BOPP films, but trans‐crystals are necessary to form the craters. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3555–3564, 2013