Nanohole structure prepared by a polystyrene-block-poly(methyl methacrylate)/poly(methyl methacrylate) mixture film

Cylindrical nanoporous structures were prepared by using a mixture film of polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) and PMMA homopolymer (hPMMA), and they were analyzed by transmission electron microtomography (TEMT), X-ray reflectivity (XR), and grazing incidence small-angle X-ray scattering. For this purpose, the mixture film was spin-coated onto a silicon wafer modified by a neutral brush for PS and PMMA blocks, which generates PMMA cylindrical microdomains oriented normal to the substrate. Two methods were employed to prepare nanoporous structures: (1) all of the PMMA phase (PMMA block and PMMA homopolymer) in the film was removed by UV irradiation, followed by rinsing with a selective solvent (acetic acid) to PMMA and (2) only PMMA homopolymer was removed by selective solvent etching without UV irradiation. We found via TEMT and XR that the nanoporous structure in the film prepared by UV irradiation exhibited almost perfect cylindrical shape throughout the entire film thickness. However, when the film was rinsed with a selective solvent, nanoporous structures were not straight cylinders but had a funnel shape in which the diameter of nanopores located near the top of the film was larger than that located near the bottom of the film.     

Coagulation method for preparing single-walled carbon nanotube/poly(methyl methacrylate) composites and their modulus,electrical conductivity,and thermal stability

A coagulation method providing a better dispersion of single-walled carbon nanotubes (SWNTs) in a polymer matrix was used to produce SWNT/poly(methyl methacrylate) (PMMA) composites. Optical microscopy and scanning electron microscopy showed an improved dispersion of SWNTs in the PMMA matrix, a key factor in composite performance. Aligned and unaligned composites were made with purified SWNTs with different SWNT loadings (0.1–7 wt %). Comprehensive testing showed improved elastic modulus, electrical conductivity, and thermal stability with the addition of SWNTs. The electrical conductivity of a 2 wt % SWNT composite decreased significantly (>10⁵) when the SWNTs were aligned, and this result was examined in terms of percolation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3333–3338, 2003     

Morphological,thermal, and conductivity studies of poly(methyl methacrylate)/polyaniline dodecylbenzenesulfonate blends

Soluble in organic solvent polyaniline (PANI) was prepared using DBSA as a functional dopant. Miscibility was maximized for PMMA with hydroquinone. Transmission electron micrographs showed lowest level of phase separation. Thermal studies by differential scanning calorimetry show some peak shifts which indicate the miscibility of two polymers. The formations of new bonds are also confirmed by Fourier transformation infrared spectroscopy. Electroconductivity increased with increase of content of doped PAN1, showing percolation threshold at 3 wt %.     

Conformational changes of poly(ethylene oxide) in poly(ethylene oxide)/poly(methyl methacrylate) blends by supercritical carbon dioxide

The effects of supercritical carbon dioxide (SC CO₂) fluids on the morphology and/or conformation of poly(ethylene oxide) (PEO) in PEO/poly(methyl methacrylate) (PMMA) blends were investigated by means of differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and Fourier transform infrared (FTIR). According to DSC data for a given blend, the melting enthalpy and, therefore, degree of crystallinity of PEO were increased, whereas the melting temperature of PEO was decreased, with SC CO₂ treatment. The enhancement of PEO crystallization with SC CO₂ treatment, as demonstrated by DSC data, was supported by WAXD data. According to FTIR quantitative analyses, before SC CO₂ treatments, the conformation of PEO was transformed from helix to trans planar zigzag via blending with PMMA. This helix‐to‐trans transformation of PEO increased proportionally with increasing PMMA content, with around 0.7% helix‐to‐trans transformation per 1% PMMA incorporation into the blend. For a given blend upon SC CO₂ treatments, the conformation of PEO was transformed from trans to helix. This trans‐to‐helix transformation of PEO decreased with increasing PMMA contents in the blends because of the presence of interactions between the two polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2479–2489, 2004     

Thermo-oxidative dehydrochlorination of rigid and plasticised poly(vinyl chloride)/poly(methyl methacrylate) blends

The aim of this work was to study the thermo-oxidative dehydrochlorination of rigid and plasticised poly(vinyl chloride)/poly(methyl methacrylate) blends. For that purpose, blends of variable compositions from 0 to 100 wt% were prepared in the presence (15, 30 and 50 wt%) and in the absence of diethyl-2-hexyl phthalate as plasticiser. Their miscibility was investigated by using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Their thermo-oxidative degradation at 180 ± 1 °C was studied and the amount of HCl released from PVC was measured by a continuous potentiometric method. Degraded samples were characterised, after purification, by FTIR spectroscopy and UV-visible spectroscopy. The results showed that the two polymers are miscible up to 60 wt% of poly(methyl methacrylate) (PMMA). This miscibility is due to a specific interaction of hydrogen bonding type between carbonyl groups (CO) of PMMA and hydrogen (CHCl) groups of PVC as shown by FTIR analysis. On the other hand, PMMA exerted a stabilizing effect on the thermal degradation of PVC by reducing the zip dehydrochlorination, leading to the formation of shorter polyenes.     

Miscibility and crystallization behaviors of stereocomplex-type poly(l- and d-lactide)/poly(methyl methacrylate) blends

Stereocomplex-poly(l- and d-lactide) (sc-PLA) and poly(methyl methacrylate) (PMMA) blends were prepared by solution blending at PMMA loadings from 20 to 80 mass%. The miscibility and crystallization behaviors of the blends have been studied in detail by differential scanning calorimeter. The single-glass transition temperatures (T _g) of the blends demonstrated that the obtained system was miscible in the amorphous state. It was observed that the crystallization peak temperature of sc-PLA/PMMA blends was marginally lower than that of neat sc-PLA at various cooling rates, indicating the dilution effect of PMMA on the sc-PLA component to restrain the overall crystallization process. In the study of isothermal crystallization kinetics, the reciprocal value of crystallization peak time ( \( t_{\text{p}}^{ - 1} \) ) decreased with increasing PMMA content, indicating that the addition of non-crystalline PMMA inhibited the isothermal crystallization of sc-PLA at an identical crystallization temperature (T _c). Moreover, the negative value of Flory–Huggins interaction parameter (χ ₁₂ = ?0.16) of the blend further indicated that sc-PLA and PMMA formed miscible blends.     

Fabrication, modification, and application of poly(methyl methacrylate) microfluidic chips

Poly(methyl methacrylate) (PMMA) is particularly useful for microfluidic chips with the features of low price, excellent optic transparency, attractive mechanical and chemical properties, ease of fabrication and modification, biocompatibility, etc. During the past decade, significant progress in the PMMA microfluidic chips has occurred. This review, which contains 120 references, summarizes the recent advances and the key strategies in the fabrication, modification, and application of PMMA microfluidic chips. It is expected that PMMA microchips should find a wide range of applications and will lead to the creation of truly disposable microfluidic devices.     

Fabrication and performance of poly(methyl methacrylate) microfluidic chips with fiber cores

In this work, a piece of glass fiber was inserted into the channel of a poly(methyl methacrylate) (PMMA) electrophoresis microchip to enhance the electroosmotic flow (EOF) and the separation efficiency. The EOF value of the glass fiber-containing microchannel at pH 8.2 was determined to be 4.17 x 10(-4)cm2 V(-1)s(-1). The performance of the new microchip was demonstrated by its ability to separate and detect three purines coupled with end-column amperometric detection. In addition, a piece of trypsin-immobilized glass fiber was inserted into the channel of a PMMA microchip to fabricate a core-changeable microfluidic bioreactor that can be regenerated by changing the fiber. The in-channel fiber bioreactor has been coupled with matrix-assisted laser desorption ionization time-of-flight mass spectrometry for the digestion and peptide mapping of bovine serum albumin and myoglobin.     

Thermal and mechanical behavior of amorphous and semi-crystalline poly(vinylidene fluoride)/poly(methyl methacrylate) blends

Various PVDF/PMMA (poly(vinylidene fluoride)/poly(methyl methacrylate)) blends were selected for mechanical testing in compression. At low PVDF content (less than 50/50 w/w), the blends remain amorphous and PVDF and PMMA are fully miscible. In PVDF-richer blends, PVDF crystallizes in part, leading to a PMMA-enriched homogeneous amorphous phase. In this study, the degree of crystallinity was set at equilibrium by appropriate annealing of the samples before testing. Mechanical analysis was focused on the low deformation range, and especially on the yield region. Depending on the test temperature and blend composition, three types of response were identified, depending on whether plastic deformation is influenced: 1) by the PMMA secondary relaxation motions, 2) by the PVDF/PMMA glass transition motions, or 3) by the crystallite-constrained PVDF chains.     

X‐ray photoelectron spectroscopy of miscible poly(methyl methacrylate)/poly(styrene‐co‐acrylonitrile) and immiscible poly(methyl methacrylate)/polyacrylonitrile polymer surfaces metallized by nickel

A miscible blend of poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile) and an immiscible blend of poly(methyl methacrylate) and polyacrylonitrile were metallized by nickel, and their surfaces were analyzed by X‐ray photoelectron spectroscopy. Before metallization, the heteroatom distribution at the polymer surface was very different in the miscible and immiscible blends. However, this distribution was modified during metallization, which was only possible via polymer‐bond breaking, leading to similar compositions at the two interfaces. Oxygen exhibited a better affinity with nickel than nitrogen, but nickel oxide and nickel nitride were both formed at the interface. Nickel nitride prevented the metal from diffusing into the substrate, playing the role of a barrier, thus driving the oxygen to the metal layer. Amorphous carbon was also detected at the interface as a new carbon species, but it did not have any significant influence on the changes induced in the distribution of heteroatoms at the polymer surfaces. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1408–1416, 2004     

Nanoclay and carbon nanotubes as potential synergists of an organophosphorus flame-retardant in poly(methyl methacrylate)

This study explores whether nanoparticles incorporated in polymers always act as synergists of conventional flame-retardant additives. For this purpose, two different filler nanoparticles, namely organically modified layered-silicate clay minerals or nanoclays and multi-walled carbon nanotubes, were incorporated in poly(methyl methacrylate) filled with an organophosphorus flame-retardant that acts through intumescence. Effective dispersion techniques specific to each nanoparticle were utilized and prepared samples were thoroughly characterized for their nanocomposite morphologies. Nanoclays were shown to outperform carbon nanotubes in respect of improving the fire properties of intumescent formulations assessed by cone calorimeter analysis. An intriguing explanation for the observed behaviour was the restriction of intumescence by strong carbon nanotube networks formed on the flaming surfaces during combustion contrary to enhanced intumescent chars by nanoclays. Carbon nanotubes surpassed nanoclays considering the thermal stability of intumescent formulations in thermogravimetry whereas mechanical properties were significantly superior with nanoclays to those with carbon nanotubes.     

Thermal properties of single walled carbon nanotubes composites of polyamide 6/poly(methyl methacrylate) blend system

The nanocomposites of polyamide 6 (PA6)/poly(methyl methacrylate) (PMMA)/non-functionalized and functionalized [carboxylic acid (COOH) and hydroxyl (OH)] single wall carbon nanotubes (SWCNTs) were prepared in mass ratios of 79.5/19.5/1, 49.5/49.5/1, and 19.5/79.5/1 by melt–mixing method at 230 °C. The PA6/PMMA blends with mass ratios of 80/20, 50/50, and 20/80 served as references. The Fourier transform infrared analyses of nanocomposites showed the formation of hydrogen bond interactions among PA6, PMMA, and OH and COOH functional groups of SWCNTs. The nanocomposites and blends had higher thermal stability with respect to the PMMA. The differential scanning calorimeter (DSC) curves showed that the nanocomposites and blends exhibited two T _g values at around 51 and 126 °C for PA6 and PMMA, respectively. About 20 °C early crystallization was observed in nanocomposites compared to the blends. The dynamic mechanical analysis (DMA) results suggested that among all the compositions of blends and nanocomposites, storage modulus (E′) was higher for PMMA-rich blends and nanocomposites. At 25 °C, the E′ values were higher for blends and nanocomposites compared to the neat PA6. The tan δ curves indicated that the more heterogeneity of the hybrid nature resulted in PA6/PMMA/SWCNTs-OH or SWCNTs-COOH with 79.5/19.5/1 mass ratio nanocomposites compared to the PA6/PMMA with 80/20 mass ratio blend. The higher T _g values of PA6 and PMMA were observed in DMA studies compared to the DSC studies for PA6 and PMMA as neat and in blends and nanocomposites. The significant improvements in crystallization of nanocomposites were considered resulting from achieving better compatibility among the polymer components and carbon nanotubes.     

The structure and properties of drawn blends of poly (vinylidene fluoride) and poly (methyl methacrylate)

A blend consisting of equal proportions of poly (vinylidene fluoride) and poly (methyl methacrylate) has been prepared and drawn to draw ratios up to 7. The mechanical properties and the structure and morphology of the samples have been measured, the latter using differential scanning calorimetry, optical microscopy, and various x-ray techniques. A structural model is proposed for the drawn materials which accounts for the mechanical properties and for the response of the crystalline regions of the material to an applied stress.     

Relationship between structure and dielectric behavior of stereoregular poly(methyl methacrylate) in the glassy state

In order to elucidate the relationship between dielectric behavior and structure in solid polymers, we studied the dielectric relaxation of stereoregular poly(methyl methacrylate) (PMMA) in the glassy state. Assuming that the extremes of molecular structure are attained in the crystal and in solution, the most probable conformation of the main chain in the glassy state is estimated for isotactic and syndiotactic PMMA in terms of conformational analysis, the unperturbed mean-square end-to-end distance in solution, and the NMR second moment in the glassy state. Under the assumption that the molecular structure varies in a limited range near the most probable conformation and that the α-methyl group rotates freely, the energy barrier for the rotation of the side group is calculated. With the calculated energy barrier, the dielectric relaxation due to the side group is interpreted fairly satisfactorily by the barrier theory of Hoffman and Lauritzen, although the width of the relaxation curve is not. The experimental result that the loss peak of syndiotactic PMMA is located at higher temperature than that of isotactic PMMA is interpreted qualitatively in terms of different conformations for the syndiotactic and isotactic chains.     

Phase equilibria of PS with PMMA and poly(co‐methyl methacrylate and styrene)mers

The available literature data on the phase equilibrium in the systems PS ‐ PMMA and PS ‐ (MMA‐S) copolymers of various compositions are ambiguous. The most contradictory results were obtained for mixtures formed from solutions [1‐3]: This fact can result, first, from the low compatibility of the polymers, which borders on the sensitivity of the testing methods used, and second, from specific interactions between the components. In the present work, the polymer compatibility was studied using an optical interferometer [4]. The sensitivity of this method is limited by the translational mobility of molecules, ∼10⁻⁹ cm²/s, so the measurements were carried out at high temperatures close to the destruction temperatures of PMMA and its copolymers. The specific feature of optical interferometry is that the studies are carried out in thin layer; this enables visual separation and estimation of the effect of the destruction products and the destruction process on the compatibility of polymers. Therefore, the purpose of this work was to study the effect of the thermal destruction products on the interference of the destructed polymer and on the diffusion transition zone of polymers in order to obtain the most complete data on the compatibility of the polymers over a broad composition range.     

Competition between poly(methyl methacrylate) and poly(ethylene glycol) during their interaction with poly(silicic acid) in an organic solvent

It is shown that the interpolymer complex of poly(silicic acid) and poly(ethylene glycol) formed in the organic solvent benzene is thermodynamically more stable than the corresponding complex with PMMA. Therefore, poly(silicic acid) prepared via template polycondensation conducted in the presence of poly(ethylene glycol) contains a smaller amount of defects (branches and crosslinks) than the same polymer obtained in the presence of PMMA. To provide evidence for the interaction between poly(silicic acid) and PMMA, the dynamic light-scattering method with the use of “invisible” macromolecules has been applied for the first time.     

Interactions between dextran-modified poly(methyl methacrylate) latex particles and concanavalin A

The electrostatic and affinity interactions between concanavalin A (Con A) and dextran-modified latex particles were investigated. The ratio of the initial number of dextran active sites to that of Con A molecules plays an important role in determining the structure of flocs formed during adsorption and, thereby, has an influence on the amount of adsorbed Con A and the subsequent elution yield. NaCl and d-glucose, used successively in the two-step desorption of Con A, were employed to study the relative importance of electrostatic and affinity interactions involved in the Con A adsorption process. A significant fraction of adsorbed Con A is attributed to the electrostatic interaction mechanism. The feasibility of using the dextran-modified latex products to purify Con A from Jack bean meal was demonstrated. Received: 22 February 2000 Accepted: 19 September 2000     

Thermorheological complexity of poly(methyl methacrylate)/poly(vinylidene fluoride) miscible polymer blend: Terminal and segmental levels

Oscillatory shear rheometry data for a miscible blend of 20 wt % poly(vinylidene fluoride) (PVDF) in poly(methyl methacrylate) (PMMA) shows breakdown of time–temperature superposition for this blend. A comparison between glass transition temperature which PMMA chains sense in the blend and effective glass transition temperature of this component indicates that, the Lodge–McLeish model can describe terminal dynamics of PMMA. In addition, terminal dynamics of PVDF chains in the blend is similar to that of its pure state in agreement with the mentioned model. At segmental level, dynamic mechanical thermal analysis of four wholly amorphous blends suggests that cooperativity of molecular motions decreases upon addition of 30 and 40 wt % PVDF to PMMA. This behavior has been confirmed via calculation of degree of fragility which presumably is attributed to strong tendency of PVDF chains to self‐association rather than inter‐association with PMMA chains according to the FTIR results. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2860–2870, 2007     

Relation between free radicals and ultraviolet absorption in poly(methyl methacrylate)

A correlation between the radiation-induced nine-line electron spin resonance signal and the unstable component of the optical absorption in the near ultraviolet in poly(methyl methacrylate) is made on the basis of the radiation dose relationship, the dependence of production on irradiation temperature at a constant radiation dose, and on the fading of both signals on oxygen diffusion into the poly(methyl methacrylate) after irradiation. It is concluded that this correlation is applicable only immediately after irradiation and the stability of the initial radical is discussed with respect to the fading results. A process of radical decay and conversion is suggested to account for differences found in the fading characteristics of the two signals.