A new method in designing compatibility and adhesion of EVA/PMMA blend by using EVA-<Emphasis Type="Italic">g</Emphasis>-PMMA with controlled graft chain length

Atom transfer free radical polymerization (ATRP) was employed in a synthesis of graft polymer EVA-g-PMMA with controlled length of side PMMA chains. Three steps of synthesis: partial hydrolysis of EVA, esterification with chloroacetyl chloride and ATRP grafting were performed to produce EVAOH, macroinitiator EVACl and grafted polymers G8020 (EVA/PMMA?=?80/20 wt%) and G6040 (EVA/PMMA?=?60/40 wt%). FTIR, Raman and NMR spectroscopy were used in the determination of the chemical structure and modification of EVA. Transmitted light and dark field microscopy showed higher affinity for coil formation of EVA-g-PMMA with longer PMMA side chains, i.e. G6040 compatibilizer. Morphological, thermal and adhesive properties of optical fiber adhesives of graft polymers and polymer blends poly(ethylene-co-vinyl acetate)-blend-poly(methyl methacrylate) (EVA/PMMA) compatibilized with 1 wt% of EVA-g-PMMA, were studied. Image analysis of SEM micrographs showed effective compatibilization with short grafted chains (G8020) that was indicated by lower porosity characteristics. TG/DTG analysis enabled determination of degree of hydrolysis and amount of chloro-functionalized groups. DSC analysis showed higher thermal stability of G8020 polymer. Single lap joint of adhesives/optical fibers were subjected to adhesive testing and obtained results for maximal force applied and adhesive failure suggested the visible influence of the length of graft chains on adhesion.     

Aqueous lubricating properties of charged (ABC) and neutral (ABA) triblock copolymer chains

Application of charged polymer chains as additives for lubricating neutral surfaces in aqueous environment, especially via polymer physisorption, is generally impeded by the electrostatic repulsion between adjacent polymers on the surface. In this study, we have investigated the adsorption and aqueous lubricating properties of an amphiphilic triblock copolymer, comprised of a neutral poly(ethylene glycol) (PEG) block, a hydrophobic poly(2-methoxyethyl acrylate) (PMEA) block, and a charged poly(methacrylic acid) (PMAA) block, namely PEG-b-PMEA-b-PMAA. After adsorption onto a nonpolar hydrophobic surface from aqueous solution, an equal and homogeneous mixture of neutral PEG and charged PMAA chains is formed on the surface, with an adsorbed polymer mass comparable to its fully neutral counterpart, PEG-b-PMEA-b-PEG. The lubricity of PEG-b-PMEA-b-PMAA showed significant improvement compared to fully charged polymer chains, e.g. poly(acrylic acid)-block-poly(2-methoxyethyl acrylate) (PAA-b-PMEA), which is attributed to dilution of charged moieties on the surface and subsequent improvement of the lubricating film stability.     

Adsorbing polymers and viscosity of cement pastes

In this paper, we study the physical mechanisms at the origin of a decrease in viscosity of concentrated cement pastes containing adsorbing polymers. We suggest from our results, similar to other authors, that plasticizers are able to decrease viscous dissipation by modifying the flocculation state of the system, which, in turn, impacts the way shear localizes. Our experimental results suggest that shear concentrates in fluid layers, the thickness of which scales with the surface-to-surface separating distance between cement grains imposed by the adsorbed polymer conformation. These effects being identical for all polymers, we suggest that the residual difference between polymers in the final macroscopic viscosity comes from the more or less pronounced increase in the local viscosity of the interstitial fluid between neighboring particles. This increase could either be correlated to the concentration of non-adsorbed coils in the interstitial fluid or to the local concentration of adsorbed coil side chains.     

支化结构对树枝状聚合物静态吸附特征的影响

采用浸泡法研究了不同支化程度的驱油用树枝状聚合物在石英砂上的静态吸附特征,并利用动静态激光光散射仪和环境扫描电子显微镜测定了聚合物溶液的分子尺寸和微观结构。结果表明,不同支化程度的树枝状聚合物溶液的等温吸附曲线均呈现三段式的吸附特点;在初始阶段,支化结构小的聚合物支链条数较少以及流体力学半径较小,其在固定表面积的石英砂上吸附位阻比支化结构大的聚合物小,导致吸附量较大;在吸附形式为多层吸附的Ⅱ、Ⅲ阶段,支化程度大的聚合物支化链间相互作用越强,易缠结形成网络结构,致使其在石英砂表面吸附层数多,吸附量比支化程度小的聚合物多。     

Surface properties of some styrene/vinyl pyridine diblock polymers adsorbed on rutile

Inverse gas chromatography (IGC) has been applied for the surface characterization of styrene-4-vinyl pyridine (S-4VP) diblock polymers of varying composition and of two rutile pigments. The latter were used as adsorbents for the polymers. Dispersion surface energies and acid-base interaction parameters were obtained from the IGC data. These show that the adsorbed layers form interphases where the local composition varies with the mass of adsorbed polymer and also with the acid-base interaction between rutile and the polymer. The results may be rationalized by suggesting that the more basic 4VP moiety preferentially orients to the acidic rutile surfaces, leaving surface compositions enriched in the less basic polystyrene (PS), which also has a lower surface energy. The effect was more pronounced when the strength of acid-base forces at the interface was increased. The experimental findings also permit the calculation of thicknesses for the adsorbed interphases. These were found to be in the range 30-90 nm, depending on the mass of adsorbed polymer and on its acid-base interaction with the adsorbing pigment surface.     

Preparation of biopolymeric micropatterns via non-residual-layered imprinting technique and its application to modify single-celled microelectrodes

Summary  A ‘‘patch clamp’’ microelectrode modified on the surface for single cell adhesion and growth was developed using a novel polymer-transfer technique to deposit cell-adhesive polymer layers on the substrate platform. Several hydrophilic polymers–-polyvinyl pyrrolidone, chitosan, alginic acid, and gelatin were successfully transferred onto the platform in order to enhance cell adhesion. The process was developed to apply a PDMS stamp pre-adhered with a phosphorylcholine (PC) layer on the protruding areas of the pattern, followed by adsorbing an adhesive polymer to imprint the adhesive layer onto the platform. Plasma activation on the stamp, adsorbed polymers, and/or the substrate was evaluated to provide an accessible method to obtain a nanothick (about 180 nm) polymeric film without any residual layer. XPS characterization on the platform verified that the bioactive polymer was only transferred and coated on the convex surfaces of the pattern. From observing the cell adhesion on the chitosan-modified platform, the number of adhered cells on the chitosan layer was found to be greater than that on the original poly(glycidyl methacrylate) (PGMA) layer, corresponding with the prediction that chitosan can serve as the cell-adhesive layer. The modified patterns were found to confine a single cell on each convex top of the platforms.     

An exfoliated clay‐poly(norbornene) nanocomposite prepared by metal‐mediated surface‐initiated polymerization

An exfoliated clay?polymer nanocomposite was prepared by surface‐initiated ring opening metathesis polymerization (SI‐ROMP) of norbornene on a montmorillonite (MMT) clay with a modified surface. Utilizing the hydrothermal‐silylation reaction between a norbornenyl‐bearing chlorosilane agent and silanol groups of the MMT clay, we were able to bind a metal alkylidene catalyst to the surface in order to grow poly(norbornene) chains directly from the surface using ROMP. Our approach produced nanocomposites having poly(norbornene) chains that are covalently attached to the inorganic substrate, as opposed to most conventional polymer‐clay composites that have ionically tethered chains (via the ammonium‐based modifiers of the organoclay) or physically adsorbed polymers. POLYM. ENG. SCI., 55:2349–2354, 2015. © 2015 Society of Plastics Engineers     

The behavior of salt-free polyelectrolyte solutions at charged surfaces

The properties of polyelectrolytes at oppositely charged surfaces are studied using Monte Carlo (MC) simulations and integral equation theory. The polymer molecules are modeled as chains of charged spheres, the counterions and co-ions are charged spheres, and the surface is smooth and uniformly charged. The polymer concentration in the simulations is strongly peaked at the surface, and this is accompanied by a depletion of polymers at larger distances from the surface. The thickness of the adsorbed layer decreases with increasing polymer concentration or surface charge density, but the total adsorbed amount displays a non-monotonic dependence on polymer concentration. The integral equation theory predictions are in qualitative agreement with the MC results.     

Rates of the colloid coagulation in the presence of irreversibly adsorbing and non‐adsorbing polymers

We have developed an analytic self‐consistent field theory of the effective interactions between nano‐ colloids mediated by irreversibly adsorbing polymers and non‐adsorbing polymers having a gyration radius much larger than that of colloids. By making use of this theory, we have calculated the potential of the polymer‐mediated forces for the above cases of polymer adsorption. On the basis of the obtained results for the polymer‐mediated potentials, we have obtained the stability ratio and rate of the coagulation in the presence of adsorbing and non‐adsorbing polymers. As a final result of our studies, we constructed the coagulation diagram that quantifies the combined effect of the Van der Waals and polymer‐mediated forces on the rate of colloid coagulation. Kinetic stability of the material‐specific colloid systems is discussed. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Synthesis of a novel fluorene-based conjugated polymer with pendent bulky caged adamantane moieties and its application in the detection of trace DNT explosives

A novel fluorene-based conjugated polymer with phenylene spacers and steric bulky adamantane moieties in side chains has been synthesized by palladium-catalyzed Suzuki coupling reactions. This design strategy offers several advantages for the detection of trace 2,4-dinitrotoluene (DNT) vapor. The incorporation of the two groups into polymer side chains could retain an effective conjugation length and prevent the π-stacking of polymer chains. The detection of DNT vapor indicated that the polymer displayed higher fluorescence quenching sensitivity toward the explosives in films compared to reference polymers. The fluorescence quenching efficiency of the fluorescent polymer achieved 33.3% in 10 s and 71.1% in 60 s. The pathways or cavities generated by the two spacers are beneficial for the rapid diffusion of explosive vapor into the film interiors and increase the fluorescence quenching efficiency of the film.     

Properties of branched polymer chains adsorbed on a patterned surface

The aim of this study was to investigate the properties of polymer chains strongly adsorbed on a planar surface. Model macromolecules were constructed of identical segments, the positions of which were restricted to nodes of a simple cubic lattice. The chains were in good solvent conditions, thus, the excluded volume was the only interaction between the polymer segments. The polymer model chain interacted via a simple contact potential with an impenetrable flat surface with two kinds of points: attractive and repulsive (the latter being arranged into narrow strips). The properties of the macromolecular system were determined by means of Monte Carlo simulations with a sampling algorithm based on the local conformational changes of the chain. The structure of adsorbed chains was found to be strongly dependent on the distance between the repulsive strips, whenever this distance was very short. The mobility of the chains was also studied and it was found that diffusion across repulsive strips was suppressed for large distances between the strips.     

Layer-by-Layer assembly of two polyacrylate derivatives: Effect of solvent composition and side-chain structure

We fabricated Layer-by-Layer (LbL) assemblies of poly(8-(4-carboxy-phenoxy)-octyl acrylate) (PCPOA) and poly(3-(4-pyridyl)-propyl acrylate) (PPyPA) in solvent mixtures of tetrahydrofuran (THF) and ethanol with different compositions. It was confirmed by FT-IR spectroscopy that the driving force for the assembly was mainly hydrogen bonding. Effect of solvent composition on the assembly was investigated using UV-vis spectroscopy. The amount of polymers in the film initially decreased with increase of THF content in solvent mixture, reaching a minimal value in the range between 45% and 70%, and then increased with increase of THF content. Combined with the polymer radius of gyration obtained from Dissipative Particle Dynamics simulation, we found that the adsorption amount of polymer is small when conformation of polymer is extended in a solution. We also investigated the effect of the number of methylene groups in polymer side chains on LbL assembly. When poly(2-(4-carboxy-phenoxy)-ethyl acrylate) (PCPEA) was used instead of PCPOA, we found that more polymers were adsorbed onto the substrate. In addition, we compared the normalized growth curves of both assemblies and found that the deviation of (PCPEA/PPyPA)_n from linear growth was larger than that of (PCPOA/PPyPA)_n.     

粒子在溶液中吸附聚电解质行为及粒子间的相互作用(Ⅱ)数值分析和结果讨论

用Newdon -Raphson迭代法对链节密度分布模型进行数值分析 ,从理论上探讨了聚合物分子链在粒子表面的构象状况 ,聚合物分子量、分子链电荷密度、聚合物和溶剂的相互作用参数及聚合物和粒子表面相互作用参数等因素对分子链在粒子表面的吸附行为和吸附有聚合物的粒子间的相互作用的影响 ,并通过聚丙烯酰胺(PAM)和阳离子聚丙烯酰胺 (CPAM)在炭黑表面的吸附验证了所建立的模型     

The effect of copolymer composition on the surface properties of perfluoroalkylethyl acrylates

The surface properties of two perfluoroalkylethyl acrylic copolymers—aqueous, Zonyl^®329 and solvent‐based, Zonyl^®225—were studied. Zonyl^®329 is a water‐based dispersion and Zonyl^®225 a solvent‐based copolymer solution; both polymers have the same perfluoroalkyethyl side chains [F(CF₂)_nCH₂CH₂? ] but have different comonomer compositions. Thin films, prepared by dip coating onto mica and quartz, with and without annealing, were characterized by contact angle and by X‐ray photoelectron spectroscopy (XPS). The contact angle measurements showed little variation with polymer and with substrate, consistent with the supposition that the perfluoroalkylethyl chains aggregate on the surface and thus dominate surface properties, irrespective of the composition of the rest of the polymer. XPS revealed only small variations in surface chemistry for studied films. Annealed films showed improved segregation for solvent‐based Zonyl^®225, which has both hydrocarbon alkyl and perfluoroalkylethyl side chains; the presence of hydrocarbon alkyl chains enables the perfluoroalkylethyl chains to reorganize after annealing. Depending on the external conditions, this thermal treatment can enable more perfluoroalkylethyl chains to reach the film surface (solid/air interface), leading to a reduction in the dispersive‐dominant surface and enhancement in perfluoroalkylethyl segregation. This suggested that perfluoroalkylethyl side chains dominate the surface properties, which are thus not dependent on substrate, backbone composition, or formulation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Impact of polymer modulus/chain mobility on water accumulation at polymer/metal oxide interfaces

Moisture is known to accumulate at the interface between polymers and metal oxides, leading to detrimental effects on physical properties such as modulus and adhesion. Direct measurement of the interfacial moisture profile has been carried out with neutron reflectivity, while thickness dependent swelling of a thin film series has also been also utilized to indirectly assess the interfacial moisture content. In this work, the moisture adsorption on the clean surfaces is compared to that observed when the surface is coated with a series of polymer films. The mechanical properties of the polymer appear to impact the quantity of moisture adsorbed at the interface; surprisingly less moisture accumulates at the interface if the coating is rubbery (larger intrinsic mobility of polymer chains). For glassy polymers, the total accumulation at the interface is identical to the adsorption on the clean metal oxide surface. This result potentially provides an understanding of solvent distribution in glassy nanocomposites by measuring moisture adsorption onto the bare filler materials prior to incorporation into the polymer matrix.     

Effect of molecular weight on the dissolution properties of polystyrene latex films

An in situ steady-state fluorescence (SSF) technique was applied in order to study the dissolution process of polystyrene (PS) latex films. The effect of the molecular weight M _w of the PS on the dissolution rate was investigated. The PS chains were copolymerized with (1-pyrene)methyl methacrylate in order to make use of pyrene (P) as a fluorescent probe to monitor the dissolution process. Seven different films were prepared from P-labeled PS latex dispersions with different molecular weights at room temperature. These films were then annealed at 200 °C for 15 min to complete the film formation process before dissolution. The dissolution of PS films in a toluene (70 %)–cyclohexane (30 %) mixture was monitored in real time by watching the change in the fluorescence intensity of P, I _P. We used a model that included both case I and case II diffusion kinetics to interpret the results of the dissolution experiments. The relaxation constants k ₀ and the dissolution coefficients D _d of the polymer chains were measured. Two different dissolution coefficients were obtained, which were attributed to the small and long polymer chains in the film, considering the high polydispersity of the polymer. It was also found that both of the D _d values scaled with M _w according to the law D _d ≈ M ^?n .     

Ultra-thin films of cationic amphiphilic poly(2-(dimethylamino)ethyl methacrylate) based block copolymers as surface wettability modifiers

Ultra-thin films of cationic amphiphilic block and statistical copolymers were applied on silica surfaces from aqueous solutions through electrostatic interactions, and the resulting modification in the wettability of the surfaces was studied. A copolymer series from 2-(dimethylamino)ethyl methacrylate with methyl methacrylate and butyl methacrylate was polymerized by ATRP. Subsequently, the conformation of the polymers in aqueous solutions was studied by surface tension measurements, dynamic light scattering, ¹H NMR and cryogenic transmission electron microscopy. Unimeric conformation, equilibrium micelles or frozen micellar structures were observed, depending on polymer composition and the ionic strength of the solution. The polymers were applied on silica from aqueous solutions by either spin coating or adsorption. The formed ultra-thin film surfaces were studied by AFM and water contact angle measurements. The spin-coated surfaces were highly hydrophilic with rapidly dropping contact angles, whereas the surfaces prepared by adsorption had stable water contact angles between 30-60°, depending on polymer. The difference between the spin-coated and adsorbed surfaces is explained by the formation of a monolayer in the adsorbed surfaces.     

Direct synthesis of polymer-grafted inorganic hybrids via reversible chain transfer catalyzed polymerization

In this work, a new simple and robust method for preparation of polymer-grafted inorganic hybrids through “grafting to” reaction is presented. Polymer chains were synthesized by reversible chain transfer catalyzed polymerization (RTCP) are capped with iodine according to the RTCP mechanism. The obtained iodine-capped polymer chains can react irreversibly with the hydroxyl groups available on the surface of inorganic materials through a nucleophilic substitution (SN) reaction. In this method, there is no need to modify the surface of inorganic materials or to functionalize polymer chains prior to the “grafting to” reaction. RTCP produced polystyrenes with different molecular weights, e.g., 4,000, 6,000, and 8,000 g/mol, and silica nanoparticles were employed as the polymer and inorganic materials, respectively. The resulting hybrids were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, and transmission electron microscopy techniques. According to the results, graft density decreased by increasing the polystyrene molecular weight. Additionally, the rheological studies of prepared polystyrene nanocomposites containing 2 wt % of the produced hybrids confirmed the better dispersion of the modified hybrids in the polystyrene matrix. The glass transition temperature (T _g) of the polystyrene nanocomposites was driven by differential scanning calorimeter technique. Analysis of nanocomposites’ T _g results revealed that increment of the grafted polymer molecular weight of hybrids increased the glass transition temperature of the prepared nanocomposites due to improvement of the dispersion level.     

Polymer-polymer composites fabricated by the in situ release and coalescence of polymer chains from their inclusion compounds with urea into a carrier polymer phase

Inclusion compounds (ICs) can be formed between small-molecule hosts and guest polymers, where the crystalline host lattice confines the guest polymers to occupy narrow cylindrical channels. The included polymers are highly extended by the narrow channel diameters and are separated from neighboring polymer chains by the walls of the small-molecule host lattice. It is possible to coalesce the polymer chains from their ICs by exposure to a solvent for the small-molecule host which is not a solvent for the included polymer chains. When crystallizable polymers are coalesced from their ICs by solvent treatment, they are observed to crystallize in an extended-chain morphology accompanied by much less chain-folding than occurs when crystallization of the same polymers take place from their disordered melt or solution environments. In this report we outline our initial efforts to create polymer-polymer molecular composites based on the coalescence of polymer chains from their IC crystals with urea, which were previously embedded in a carrier polymer phase. Both film and fiber composites made with chemically identical or distinct IC-included and carrier polymers are described. Water vapor permeation, differential scanning calorimetry (DSC) and microscopic observations are used to probe these composites; and several applications are suggested. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 281–287, 1997     

Antigraffiti polyurethane coating containing fluorocarbon side chains grafted polymethylsiloxane

The novel polymethylsiloxane grafted by fluorocarbon side chains was synthesized via hydrosilylation reaction of polymethylhydrosiloxane (PMHS) with 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) in the presence of Karstedt’s catalyst. The reaction factors of reaction temperature, reaction time, catalyst dosage, solvent dosage, and molar ratio of the reactants were investigated through orthogonal experiments. Under optimal conditions, the grafting ratio of HFBA to PMHS reached 91.6%. The structure of the grafted polymer was characterized by FTIR and ¹H NMR spectra. The synthesized polymer was incorporated into two-component polyurethane coating formulations as an additive to prepare antigraffiti coatings. After curing, the contact angle measurement was performed and the results showed that surface free energy of the coating film decreased dramatically from 30.7 to 21.4 mJ/m². The inks of permanent markers cannot spread readily on the coating film and can be removed easily, indicating that the incorporation of the synthesized polymer endowed the coating with admirable antigraffiti performance. XPS analysis revealed that atomic concentrations of silicon and fluorine near the surface (about 10 nm) were much higher than deeper within the film (about 100 nm), suggesting that these two elements had a strong migration tendency toward the coating–air interface. AFM measurement showed that the inclusion of synthesized polymer in coating did not affect the surface roughness of the film.