Mixed monolayers of pmas with poly(styrene‐b‐methyl methacrylate) at the air/water interface

Poly(methyl methacrylate) (PMMA) is known to be immiscible with poly(styrene) (PS) in the bulk state. Poly(ethyl methacrylate) (PEMA), poly(propyl methacrylate) (PPMA), and poly(n‐butyl methacrylate) (PBMA) are also known to be immiscible with PMMA (or PS). Therefore, PMAs (PMMA, PEMA, PPMA, and PBMA) are predicted by the mean field theory to be immiscible with poly(styrene‐b‐methyl methacrylate) (PS‐b‐PMMA) in the bulk state. However, the miscibility of PMAs with PS‐b‐PMMA may be different in the two‐dimensional state. Therefore, the mixed monolayer behavior of PMAs and PS‐b‐PMMA was investigated from the measurements of surface pressure‐area per molecule (π‐A) isotherms at three different temperatures (10°C, 25°C, and 40°C). Calculation of compressibility from isotherms provided the inflection data from maximum and minimum peaks. The miscibility and nonideality of the mixed monolayers were examined by calculating the excess area as a function of composition. Mostly, negative deviations from ideality were observed in the mixed monolayers. This is likely because of favorable interaction between PMMA and PMAs in the monolayer state. The positive deviations occurred at 40°C with PBMA at a high surface pressure. Therefore, with confinement in the two‐dimensional state, the miscibility between PMAs and PS‐b‐PMMA was greatly improved in comparison with the bulk state. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Miscibility of mixed stereoregular PMMA/PVCN monolayers at the air/water interface

The mixed monolayer behavior of stereoregular poly(methyl methacrylate) (PMMA) and poly(vinyl cinnamate) (PVCN) was investigated from the measurements of surface pressure–area per molecule (π–A) isotherms at three different temperatures of 25 ± 1, 32.5 ± 1, and 40 ± 1°C. The miscibility and nonideality of the mixed monolayers were examined by calculating the excess area as a function of composition. Positive and negative deviations from ideality were observed. Negative deviations were observed mostly in syndiotactic PMMA (sPMMA) and PVCN blends suggesting the existence of favorable interactions. However, positive deviations in most isotactic PMMA (iPMMA) and PVCN blends indicated that the existence of unfavorable interactions. Atactic PMMA and PVCN blends demonstrated intermediate deviation behavior to sPMMA and iPMMA blends. On the basis of the results of π–A isotherms, the monolayer miscibility between PMMA and PVCN was in the majority not in agreement with the studies on the same blends in the bulk state. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characteristics and iso‐baric relaxation phenomenon of pmma monolayers with different molecular weights at different temperatures

Poly(methyl methacrylate) (PMMA) monolayers with different molecular weights at the air/water interface were investigated at three different temperatures. The monolayer characteristics of PMMA were studied in terms of surface pressure‐area per molecule (π‐A) isotherm and isobaric relaxation experiments. The results show that the π‐A isotherms of PMMA converge at 40°C regardless of molecular weight. The collapse pressure of PMMA monolayers decreases as the temperature is elevated. It was shown the area relaxation process of PMMA could be described by a model considering the nucleation and growth mechanisms. The simulation parameters of area relaxation of PMMA with different molecular weights at 8 mN/m are very similar, indicating similar mechanisms. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of additives on the morphologies of thin titania films from self-assembly of a block copolymer

The effects of additives of poly(methyl methacrylate) (PMMA) and HAuCl₄ on the morphologies of hybrid titania films formed via co-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers, titania sol-gel precursor in a selective solvent were investigated. The results show that addition of PMMA or HAuCl₄ has an important influence on the morphologies of hybrid titania films. Addition of PMMA or HAuCl₄ can induce the morphology transition of the PS-b-PEO/titania sol-gel mixture from spherical micelles to vesicles. Therefore, the morphologies of the hybrid films formed on silicon substrate surfaces by spin-coating can be controlled by the addition of homopolymer (PMMA) or inorganic precursor (HAuCl₄) into the PS-b-PEO/titania sol-gel mixtures, allowing access to nanoparticles or nanoporous films. After removing the polymer matrix, nanoparticle aggregates or nanobowl-like structures are left behind on the substrate surfaces.     

Morphology of polystyrene/polystyrene-block-poly(methyl methacrylate)/poly(methyl methacrylate) composite particles

Polystyrene/polystyrene-block-poly(methyl methacrylate)/poly(methyl methacrylate) (PS/PS-b-PMMA/PMMA) composite particles were prepared by releasing toluene from PS/PS-b-PMMA/PMMA/toluene droplets dispersed in a sodium dodecyl sulfate aqueous solution. The morphology of the composite particles was affected by release rate of toluene, the molecular weight of PS-b-PMMA, droplet size, and polymer composition. ‘Onion-like’ multilayered composite particles were prepared from toluene droplets of PS-b-PMMA and of PS/PS-b-PMMA/PMMA, in which the weights of PS and PMMA were the same. The layer thicknesses of the latter multilayered composite particles increased with an increase in the amount of the homopolymers. PS-b-PMMA/PS composite particles had a sea-islands structure, in which PMMA domains were dispersed in a PS matrix. On the other hand, PS-b-PMMA/PMMA composite particles had a cylinder-like structure consisting of a PMMA matrix and PS domains.     

Synthesis and analysis of phase segregation of polystyrene-block-poly(methyl methacrylate) copolymer obtained by Steglich esterification from semitelechelic blocks of polystyrene and poly(methyl methacrylate)

Here, an alternative route to successfully synthesize polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is reported. Steglich esterification was used as an effective, metal free approach for coupling carboxylic terminated PS and the hydroxyl end-functionalized PMMA chains obtained by nitroxide-mediated polymerization and atom transfer radical polymerization, respectively. α-Functionalization was obtained using 4,4′-azobis(4-cyanovaleric acid) and 2,2,2-tribromoethanol as initiators. The synthesis of PS-b-PMMA was confirmed by gel permeation chromatography and nuclear magnetic resonance (NMR), while the dependence of the diffusion coefficients of the polymers (PS, PMMA, PS/PMMA blend, and PS-b-PMMA) with their corresponding molecular weights was discussed based on the results of atomic force microscopy-based infrared spectroscopy, differential scanning calorimetry, and spectra of diffusion-ordered NMR spectroscopy. Differently from PS-b-PMMA, a partial segregation was observed for the PS/PMMA blend, affecting its thermal behavior and diffusion coefficient. The study here presented provides an easier and efficient strategy for the synthesis of PS-b-PMMA and new insights into the diffusion of polymers.     

Influence of molecular weight of poly (methyl methacrylate) on its miscibility with poly (vinyl chloride) in the solution

In this work, the molecular weight effect on miscibility between poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) in cyclohexanone(CH) solutions at 30 °C was examined by the viscometric method. Three samples of PMMA were prepared by emulsion polymerization, which molecular weights were changed by tert-dodecyl-mercaptan (TDDM) content. The parameter Δb is used to predict polymer-polymer miscibility of PVC/PMMA/cyclohexanone blend. Δb values indicated that the highest molecular weight of PMMA is immiscible with PVC resin. The molecular weight of PMMA decrease with the increase of the contention of TDDM, and the contribution of miscibility PVC/PMMA blend in CH is better.     

Solution blending of polystyrene and poly(methyl methacrylate)

Blends of poly(methyl methacrylate) (PMMA) and polystyrene (PS) have been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were made of a low molecular weight PS with three PMMAs having number-average molecular weights of (1) 18,300, (2) 37,000, and (3) 211,000, The blend was found to be partially miscible. The composition-dependent values of the polymer-polymer interaction parameter (g₁₂) were determined and found to be from 0.015 to 0.029 for solution casting at 25°C. The interaction parameter (g₁₂) increases with increasing PMMA molecular weights in the PMMA/PS blend systems. This result is consistent with the behavior of the glass transition temperatures and with the microscopy study which indicate that compatibility is greater in the PMMA-1/PS blends having the low molecular weight of PMMA than in the PMMA-3/PS blends having the higher molecular weights of PMMA.     

Nanostructured unsaturated polyester modified with poly[(ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)] triblock copolymer

Miscibility, crystallization and morphology of unsaturated polyester (UP) matrices, nanostructured with a poly[(ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)] (PEO-b-PPO-b-PEO) block copolymer (BCP) from 0 to 50 wt% has been investigated. Additionally, the role of each block on miscibility and morphology of cured mixtures was studied. Behaviours of non-reactive mixtures of UP thermosetting precursor with two BCPs composed of similar and strong immiscible central PPO block were compared. It was found that one BCP had PEO blocks with not enough molecular weight to compatibilize the PPO block with the UP thermosetting precursor at room temperature. Transmitted light intensity study of mixtures indicated that during curing at 35 °C no macrophase separation took place, contrary to the systems cured at temperatures equal or higher than 60 °C. Curing mixtures at 35 °C produced nanostructured matrices with almost unchanged transparency. Phase separation and miscibility of BCP with UP matrix were measured by means of DSC and DMA. AFM analysis showed worm-like morphology with diameters from 10 to 20 nm and length that evolved from 50 nm to 1 μm with increase of BCP content.     

Vesicle formation of polystyrene-block-poly (ethylene oxide) block copolymers induced by supercritical CO2 treatment

A novel route for a preparation of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) block copolymer vesicles induced by supercritical carbon dioxide (scCO₂) is demonstrated. When PS-b-PEO block copolymer solutions in tetrahydrofuran (THF) are treated with scCO₂ at 70 °C for different times, PS-b-PEO copolymers first assemble into aggregated spheres; then aggregated spheres change into large compound micelles and finally evolve into vesicles. The possible formation mechanism of the vesicles is discussed.     

Amphiphilic polysilane with poly(ethylene oxide) side chains

The synthesis of an amphiphilic polysilane with poly(ethylene oxide) grafted segments (PS-g-PEO) through the addition of an allyl-terminated poly(ethylene oxide) (AT-PEO) to poly[diphenylsilane-co-methyl(H) silane] (PSH) in a homogeneous system and using catalyst platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane is reported The process involves the activation of the polymer by microwave irradiation as a preliminary stage with the view to perform the subsequent addition stage at room temperature, when side reactions are prevented. The PS-g-PEO structure was characterized by NMR, FT-IR spectral analysis and GPC methods. The amphiphilic properties were estimated by comparison of the water sorption isotherms of the PS-g-PEO copolymer with those of the component segments. The core-shell micellization in water and the morphological aspects of the self-assembled structures were investigated by DLS and SEM. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of Amphiphilic Diblock Copolymers by DPE Method

Amphiphilic diblock copolymers, poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) and polystyrene-b-poly(acrylic acid) (PS-b-PAA), were prepared by 1,1-diphenylethene (DPE) method under mild conditions. Firstly, free radical polymerization of tert-butyl acrylate (tBA) was carried out with AIBN as initiator in the presence of DPE, giving a DPE-containing precursor, PtBA, with controlled molecular weight. Secondly, methyl methacrylate and styrene were polymerized in the presence of PtBA precursor, and PS-b-PtBA and PMMA-b-PtBA diblock copolymers with controlled molecular weights were obtained respectively. Finally, amphiphilic diblock copolymers, PMMA-b-PAA and PS-b-PAA, were prepared by hydrolysis of PS-b-PtBA and PMMA-b-PtBA. The formation of PS-b-PAA and PMMA-b-PAA was confirmed by ¹H NMR. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to detect the self-assembly behavior of the amphiphilic diblock polymers in tetrahydrofuran (THF).     

Synthesis and thermal characterization of macromonomeric azo initiator containing poly(ε-caprolactone): Styrene and methyl methacrylate copolymerization

Macromonomeric azo initiator containing biodegradable poly(ε-caprolactone, (PCL) was synthesized by the condensation reaction of PCL with 4,4′-azobis(4-cyanopentanoyl chloride) and methacryloyl chloride. This macromonomeric azo initiator (MIM–PCL) was further used in the polymerization of styrene (St) or methylmethacrylate (MMA) via a radical initiated process at 60°C in bulk in order to obtain polystyrene (PS)-b-PCL or poly(methyl methacrylate) (PMMA)-b-PCL crosslinked block copolymers. Thermal decomposition kinetics of MIM–PCL and its copolymers were studied by using thermogravimetric analysis and differential scanning calorimetry (DSC). DSC traces of MIM–PCL showed two different exotherms, at 98 and 127°C. The first exotherm, observed at 98°C, was due to the polymerization of the terminal methacrylic groups; the other was due to the exothermic decomposition of azo groups of MIM–PCL. PCL-b-PS and PCL-b-PMMA crosslinked block copolymers showed single glass transition temperatures due to the compatibility of the crosslinked block segments. The polymer–solvent interaction parameter of PCL in chloroform was determined by vapor pressure osmometry to be 0.1 for the PCL–chloroform system at 30°C. The average molecular weights between junction points of crosslinked homo PCL were calculated by using the Flory–Rehner equation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1149–1157, 1998     

Effect of tacticity of poly(methyl methacrylate) on the miscibility with poly(vinyl pyrrolidone)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMA) (designated iPMMA, aPMMA, and sPMMA) with approximately the same molecular weight were mixed separately with poly(vinyl pyrrolidone) (PVP) primarily in chloroform to make three polymer blend systems. Differential scanning calorimetry (DSC) was used to study the miscibility of these blends. The results showed that the tacticity of PMMA has a definite impact on its miscibility with PVP. The aPMMA/PVP and sPMMA/PVP blends were found to be miscible because all the prepared films showed composition-dependent glass-transition temperatures (T_g). The glass-transition temperatures of the aPMMA/PVP blends are equal to or lower than weight average and can be qualitatively described by the Gordon–Taylor equation. The glass-transition temperatures of the other miscible blends (i.e., sPMMA/PVP blends) are mostly higher than weight average and can be approximately fitted by the simplified Kwei equation. The iPMMA/PVP blends were found to be immiscible or partially miscible based on the observation of two glass-transition temperatures. The immiscibility is probably attributable to a stronger interaction among isotactic MMA segments because its ordination and molecular packing contribute to form a rigid domain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3190–3197, 2001     

Effect of miscibility on migration of third component in star‐like co‐continuous and disperse‐within‐disperse mixed brushes

Novel ternary mixed‐brush single crystals were designed with disperse‐within‐disperse and star‐like co‐continuous morphologies based on poly(ethylene glycol) (PEG)‐b‐polystyrene (PS)/PEG‐b‐poly(methyl methacrylate) (PMMA)/PEG‐b‐polyaniline (PANI) and PEG‐b‐PS/PEG‐b‐PMMA/PEG‐b‐(poly(?‐caprolactone) (PCL) or poly(l ‐lactide) (PLLA)) block copolymers, respectively. In the disperse‐within‐disperse ternary mixed brushes, PANI nanorods were dispersed within the matrix (PS)–dispersed (PMMA) amorphous brushes. The flexibility and rigidity of brushes mainly affected the ultimate morphology and arrangement of amorphous coiled brushes in the vicinity of PANI nanorods. In addition, the migration of PCL and PLLA crystallizable brushes was evident into PMMA phases dispersed in the PS matrix, leading to star‐like co‐continuous patterns of PCL and PLLA brushes. This phenomenon was related to the miscibility of crystallizable PCL and PLLA brushes with the PMMA phase. The migration of crystallizable PCL and PLLA brushes increased the size of PMMA domains in the star‐like co‐continuous patterns. Despite the larger osmotic pressure of PLLA brushes, their higher miscibility with PMMA chains reflected the greater PMMA dispersal and wider PLLA star‐like branches. © 2017 Society of Chemical Industry     

Gas chromatographic determination of the interaction parameter of poly(ethylene oxide)/poly(methyl methacrylate) blends

Inverse gas chromatography (IGC) has been used to investigate thermodynamic miscibility of a molten poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blend. Toluene, benzene, and chloroform have been employed as probes in pure and mixed stationary phases of these polymers. Experimental measurements have been taken over a narrow range of temperatures because of the high PMMA glass transition temperature as well as the degradation of the PEO. The interaction parameter χ₂₃ determined at 150°C is slightly negative and dependent on the interacting probe, as has been also noted in previous chromatographic studies on polymer-polymer miscibility. The last section is devoted to a model calculation, using Flory's equation of state theory. Different χ₂₃-concentration curves have been simulated, with the interaction energy parameter X₂₃ as an adjustable parameter.     

Dispersion of polymer-grafted magnetic nanoparticles in homopolymers and block copolymers

The dispersion of magnetic nanoparticles (NPs) in homopolymer poly(methyl methacrylate) (PMMA) and block copolymer poly(styrene-b-methyl methacrylate) (PS-b-PMMA) films is investigated by TEM and AFM. The magnetite (Fe₃O₄) NPs are grafted with PMMA brushes with molecular weights from M = 2.7 to 35.7 kg/mol. Whereas a uniform dispersion of NPs with the longest brush is obtained in a PMMA matrix (P = 37 and 77 kg/mol), NPs with shorter brushes are found to aggregate. This behavior is attributed to wet and dry brush theory, respectively. Upon mixing NPs with the shortest brush in PS-b-PMMA, as-cast and annealed films show a uniform dispersion at 1 wt%. However, at 10 wt%, PS-b-PMMA remains disordered upon annealing and the NPs aggregate into 22 nm domains, which is greater than the domain size of the PMMA lamellae, 18 nm. For the longest brush length, the NPs aggregate into domains that are much larger than the lamellae and are encapsulated by PS-b-PMMA which form an onion-ring morphology. Using a multi-component Flory-Huggins theory, the concentrations at which the NPs are expected to phase separate in solution are calculated and found to be in good agreement with experimental observations of aggregation.     

Effects of substrate roughness on the orientation of cylindrical domains in thin films of a polystyrene-poly(methylmethacrylate) diblock copolymer studied using atomic force microscopy and cyclic voltammetry

This paper describes the orientation of cylindrical domains in thin films of a polystyrene-poly(methylmethacrylate) diblock copolymer (PS-b-PMMA; 0.3 as the PMMA volume fraction) on gold and oxide-coated Si substrates having different surface roughness. Atomic force microscopy images of PS-b-PMMA films having thickness similar to the domain periodicity permitted us to study the effects of substrate roughness and block affinity on domain orientation. PS-b-PMMA films on gold substrates showed metastable vertical domain orientation that was attained more slowly on rougher substrates. In contrast, the domains were horizontally oriented on oxide-coated Si regardless of surface roughness and the annealing conditions examined. In addition, cyclic voltammetry data for PS-b-PMMA films on gold substrates whose PMMA domains were etched suggested that the metastable vertically oriented domains reached the underlying substrates. These results indicate that PS-b-PMMA films containing vertically oriented cylindrical domains can be obtained by using rough gold substrates upon annealing under controlled conditions.     

Synthesis of binary mixed homopolymer brushes by combining atom transfer radical polymerization and nitroxide-mediated radical polymerization

This communication describes a novel strategy to synthesize binary mixed homopolymer brushes from mixed self-assembled monolayers (SAMs) on silica substrates by combining atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP). Mixed SAMs terminated by ATRP and NMRP initiators were prepared by coadsorption of two corresponding organotrichlorosilanes from toluene solutions. Mixed poly(methyl methacrylate) (PMMA)/polystyrene (PS) brushes were synthesized by ATRP of MMA at 80 °C followed by NMRP of styrene at 115 °C. Corresponding ‘free’ initiators were added into the solutions to control the polymerizations. We have found that the brush thickness increases with molecular weight in a nearly linear fashion. For a series of binary brushes consisting of PMMA of molecular weight of 26,200 and PS of various molecular weights, we have observed a transition in water contact angles with increasing PS molecular weight after CH₂Cl₂ treatment. Moreover, binary mixed polymer brushes with comparable molecular weights for two grafted polymers undergo reorganization in response to environmental changes, exhibiting different wettabilities.