PMMA Chains Research Articles

A new method in designing compatibility and adhesion of EVA/PMMA blend by using EVA-g-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.

Synthesis and characterization of PMMA and organic modified montmorilonites nanocomposites via in situ polymerization assisted by sonication

Abstract A variety of organo-modified montmorillonite (OMMT) and poly(methylmethacrylate) (PMMA) nanocomposites (CPN) were synthetized by in situ polymerization in a chloroform solution under probe sonication at clay loadings of 3 mass%. A factorial experimental design was used to study the effects of the synthesis variables: Flory-Huggins (F-H) interaction parameters between PMMA and clay organomodifier (three grades of OMMT) and sonication energy (26.0 kJ, 30.3 kJ and 34.6 kJ), aiming clay dispersion at nanoscale levels into the polymeric matrix and improvements in CPN properties. The distinct surfactant side groups of commercial OMMT were: hydroxyl (C30B), aryl (C10A) or alkyl (C25A), considering their similar interlayer space. Multiple techniques of analysis to evaluate the level of clay dispersion were used. Small-amplitude oscillatory shear rheology (SAOS) indicated a high level of clay dispersion for the PMMA/C25A CPN and a tendency to form a percolated network structure from the low shear thinning exponent nω of complex viscosity, either at low (nω = −0.97) or high (nω = −0.83) sonication energy. However, the rheological results showed a low level of clay dispersion for PMMA/C10A (nω = −0.70) and PMMA/C30B (nω = −0.40). The F-H interaction parameter was the statistically significant factor for the shear thinning exponent nω response. X-ray diffraction (XRD) of CPN exhibited no discernible reflections for PMMA/C25A-26 kJ and PMMA/C10A-30.3 kJ CPN, suggesting that a high level of clay dispersion was achieved. Transmission electronic microscopy (TEM) images of PMMA/C25A-36.4 kJ and PMMA/C30B-26 kJ CPN showed exfoliated/intercalated and intercalated morphologies, respectively. Thermogravimetry presented a significant increase in PMMA chain scission temperature of up to 82 °C for all CPN when compared to pristine PMMA. The UV–visible transmittance of PMMA/C25A-26 kJ CPN showed to be around 4.5% lower in comparison with pristine PMMA. The CPN refractive index showed a slight reduction, which could even candidate them for new materials in optical electronic devices. The improvements in the verified properties for PMMA/C25A CPN were attributed to the lower F-H interaction parameter of C25A alkyl surfactant with chloroform when considering the others OMMT side groups. The chemical affinity of the alkyl chain to the chloroform could contribute to the diffusion of the solvent/monomer solution into the interlayer space of the clay, prior to polymerization, and then the polymer chain growth to push the layers apart.

Self-assembly and omniphobic property of fluorinated unit end-functionalized poly(methyl methacrylate)

Abstract The self-assembly behavior of fluorinated unit end-functionalized poly(methyl methacrylate) (PDFHM- ef -PMMA) in solution and its influence on the surface microstructure, elemental composition and omniphobic property of cast film was investigated in this work. Specifically, three mixed solutions of tetrahydrofuran (THF)/methanol (MeOH), THF/H 2 O and THF/H 2 O/MeOH in various compositions were employed separately as the selective solvents. In THF/MeOH solution, the aggregate morphologies of PDFHM- ef -PMMA changed gradually from core-shell spheres to worm, and then to elliptical vesicles as MeOH content increased. In THF/H 2 O solution, spherical and bowl-shaped aggregates with significantly larger sizes than those in THF/MeOH solution were favored despite lower H 2 O content. The further addition of MeOH to THF/H 2 O mixture could reduce the size of aggregate but hardly change original aggregate morphology. During the film formation process, those self-assembled aggregates in THF/MeOH solution fused with one another to form a smooth surface. When such surface was fully covered by fluorinated segments, the outstanding hexadecane and water slide-off properties and ink-resistant property required for antifouling application were demonstrated. Instead, the aggregates formed in THF/H 2 O/MeOH mixture were subjected to secondary aggregation of PDFHM- ef -PMMA chains during solvent evaporation, leading to the formation of a particulate film with poor adhesion towards glass plate and hexadecane-repellent property.

On the fracture mechanism of a symmetric interface of glassy poly(methyl methacrylate) self-healed at a temperature well below the bulk glass transition temperature

Attenuated total reflection Fourier-transformed infrared spectroscopy (ATR-FTIR) has been used for the elucidation of the molecular mechanism of fracture of weak polymer−polymer interfaces self-healed partially at a temperature (T) well below the bulk glass transition temperature (Tgbulk). For this purpose, a symmetric interface of the carbon-chain polymer such as poly(methyl methacrylate) (PMMA) has been used. It has been found that the integral intensity and the half-width of the band ν = 1725 cm−1 for the fractured PMMA−PMMA interface self-healed at T = 64 °С, i.e. at T = Tgbulk – 45 °С, are higher as compared to those for the original PMMA surface and for the PMMA surface annealed at T = Tgbulk − 45 °С. The difference found is assigned to the chain scission of interdiffused PMMA chains resulting in the creation of new chain ends and their following oxidation.

Effect of grafted graphene nanosheets on morphology evolution and conductive behavior of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends during isothermal annealing.

A facile method was developed for directly grafting poly(methyl methacrylate) (PMMA) to graphene oxide (GO) without surface modification, with the resultant insulating PMMA-g-GO nanosheets further reduced in situ to give conductive grafted reduced graphene oxide (RGO) nanosheets. The effect of PMMA-g-RGO nanosheets on the morphological evolution and conductive behavior of partially miscible blends of poly(methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMA/SAN) upon annealing above their phase-separation temperature was investigated using phase-contrast microscopy (PCM) with a real-time online digital picoammeter. With phase separation of the blend matrix, the well-dispersed PMMA-g-RGO nanosheets in the homogeneous matrix preferentially migrated to the SAN-rich phase and showed remarkably little aggregation. Surface grafting of PMMA-g-RGO might inhibit the aggregation of nanosheets in the blend matrix and weaken the retardation effect of nanosheets on the morphology evolution of the blend matrix. Furthermore, the percolation behavior of dynamic resistivity for ternary nanocomposites was attributed to the formation of a PMMA-g-RGO conductive network in the SAN-rich phase. The activation energy of conductive pathway formation was closer to the activation energy of flow for PMMA than that of SAN.

Multiple-shape memory behavior of nanocomposite based on polymethylmethacrylate/poly (lactic acid)/graphene nanoplatelets (PMMA/PLA/GNP)

In this study, nanocomposite samples based on polymethylmethacrylate/poly (lactic acid)/graphene nanoplatelets (PMMA/PLA/GNP) were prepared via melt mixing method and thermal multiple shape memory was induced. Dynamic mechanical thermal analysis results showed that two polymers are miscible in the selected blend ratio (70/30, 50/50, 30/70 w/w; PLA/PMMA) and was not affected by the presence of GNP (1 and 2 phr). The dispersion and distribution status of GNP were observed by scanning electron microscopy (SEM). The co-continuous morphology was dominant in all samples due to complete miscibility of two phases. Multi-shape memory was induced using a tensile test machine equipped with the hot oven at 65 and 100 °C. The results revealed that shape recovery was affected by the presence of GNP at high temperature(for example increasing from 93.34% in neat PLA/PMMA(50/50 w/w) to 96.67% in the sample containing 1 phr of GNP) while there was no considerable effect at low temperature. At high temperature, amorphous phases of two polymers are extended and un-melted chains of PMMA can be as hard segment and leads to good recovery. Due to nucleation and reinforcement effects of GNP, the higher degree of crystallization of PLA and higher storage modulus were obtained and caused to the enhancement of the shape fixity values at the presence of GNP.

Well-defined PMMA/diatomite nanocomposites by in situ AGET ATRP: diatomite as an appropriate replacement for clay

Mesoporous diatomite nanoplatelets were used for in situ polymerization of methyl methacrylate via activators generated by electron transfer for atom transfer radical polymerization to synthesize well-defined poly (methyl methacrylate) nanocomposites. X-ray fluorescence, FTIR spectroscopy and thermogravimetric analysis (TGA) were employed for evaluating some inherent properties of pristine diatomite nanoplatelets. In addition, structural and morphological studies were also performed by nitrogen adsorption/desorption isotherm, SEM and TEM. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography respectively. Addition of 3 wt% mesoporous diatomite leads to increase of conversion from 75 to 91%. Molecular weight of PMMA chains increases from 7213 to 9878 g.mol−1 by addition of 3 wt% mesoporous diatomite; however, polydispersity index values increases from 1.15 to 1.43. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 77.3 to 82.4 °C by adding 3 wt% of mesoporous diatomite nanoplatelets.

Synthesis and characterization of wide-scale UV–vis CUT-OFF laser filter using methyl violet-6B/PMMA polymeric composite films

Abstract Poly(methyl methacrylate) (PMMA) doped with different weight percent of methyl violet-6B (MV-6B) as polymeric films were prepared by a casting method. Different concentrations of MV-6B can affect both the crystal structure and optical properties of PMMA. The broad hump diffraction peaks present in PMMA at 2θ = 15.27°, 30.60°, and 40.69° are ascribed to amorphous PMMA. During the incorporation of MV-6B dye onto PMMA, the intense peaks of PMMA at the 2θ value of 15.27° and 30.6° became less intense, and d -spacing was changed. The X-ray results confirmed the strong electrostatic interaction of the cationic MV-6B dye with the anionic PMMA polymer. Furthermore, the transmittance of PMMA/MV-6B composites is decreased with the increase of MV-6B dopants concentrations onto the PMMA matrix; this may be attributed to the electrostatic interaction between the PMMA chains and the molecules of methyl violet-6B. MV-6B-doped PMMA possesses three distinct band gaps corresponding to the pure PMMA, and other two band gaps are for the MV-6B /PMMA composite films. PMMA/MV films with 3.333 wt% of MV-6B) showed a large scale CUT-OFF laser filter inside in the range from 190 to 670 nm. Our designed filter is a unique polymeric composite film for optoelectronic and laser applications.

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

AbstractNovel 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(ϵ‐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

Synthesis of hydrophilic carbon nanotubes by grafting poly(methyl methacrylate) via click reaction and its effect on poly(vinylidene fluoride)-carbon nanotube composite membrane properties

Surface modification of azide-decorated multiwalled carbon nanotubes (MWCNTs) with well-defined alkyne-terminated poly(methyl methacrylate) (PMMA) chains was accomplished via the combination of reversible addition fragmentation chain transfer (RAFT) and “click” chemistry. Successful attachment of PMMA onto MWCNT was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography, Raman spectroscopy, and transmission electron microscopy. The highest grafting percentage (GP) of the PMMA chains (GP=23.3%) was calculated using TGA. The effect of the PMMA-grafted-MWCNTs (MWCNTs-g-PMMA) content on the performance of the poly(vinylidene fluoride) (PVDF)-MWCNTs-g-PMMA composite membrane was studied. The MWCNTs-g-PMMA was found to be well dispersed in the PVDF composite membrane matrix because of the excellent compatibility between the PMMA and PVDF chains. The composite membranes showed improved porosity, hydrophilicity, water flux, β-PVDF content, and mechanical properties at an optimal amount of 2wt% MWCNTs-g-PMMA incorporated in the PVDF membrane matrix. In contrast, the hydroxyl functionalized MWCNTs (MWCNTs-OH) showed limited enhancement in the water flux and mechanical strength, which is mainly due to the poor dispersion of MWCNT because of the weak interaction between the MWCNT and PVDF chains. This study reveals the excellent prospect of the MWCNT-based ultrafiltration membrane with enhanced properties in water treatment applications.

Synthesis of modified Natural Rubber with grafted poly(acetoacetoxyethyl methacrylate‐co‐methyl methacrylate) and performance of derived adhesives with GTA crosslinker

The main objective of this study is to develop wood adhesives that can be cured at room temperature, based on modified natural rubber (NR) latex. Two types of modified NR, namely poly(acetoacetoxyethyl methacrylate)‐grafted NR, NR‐g‐PAAEM, and poly(acetoacetoxyethyl methacrylate‐co‐methyl methacrylate)‐grafted NR, NR‐g‐P(AAEM‐co‐MMA), were synthesized. Emulsion polymerization technique was exploited to synthesize the graft copolymers. The hydrophilicity of NR after grafting modifications was examined by means of contact angle. These results reveal that the NR become more hydrophilic after being modified with poly(acetoacetoxyethyl methacrylate), PAAEM, and/or poly(methyl methacrylate), PMMA. Adhesion properties in terms of lap shear strength were studied for wood adhesives derived from both types of NR graft copolymers, with glutaraldehyde (GTA) as the crosslinking agent. The results show that adhesives based on the NR graft copolymers gave higher lap shear strength than the NR latex adhesive. For the graft copolymers, the NR‐g‐P(AAEM‐co‐MMA) adhesive exhibited much higher lap shear strength than the NR‐g‐PAAEM adhesive. This indicates that the incorporation of PMMA chains into the NR‐g‐PAAEM molecules significantly increased the cohesive strength of the resulting adhesive, which is probably due to increased modulus and hardness of the adhesive film. POLYM. ENG. SCI., 58:1610–1618, 2018. © 2017 Society of Plastics Engineers

Reactive Compatibilization: Formation of Double-Grafted Copolymers by In Situ Binary Grafting and Their Compatibilization Effect.

Reactive compatibilizers are usually used to enhance the compatibility of immiscible polymer blends. However, reactive linear compatibilizers containing reactive groups on the main chains form graft copolymers during reactive blending, and such graft copolymers with an asymmetric molecular structure are often "pulled in" or "pulled out" under mechanical shear. Double-grafted compatibilizers have a symmetric structure, and they usually exhibit higher compatibilizing efficiency. In this work, we propose a binary grafting strategy during melt blending to form compatibilizers located at the interface of an immiscible polymer blend. Specifically, poly(methyl methacrylate) (PMMA) oligomer with carboxylic end groups (PMMA-COOH) and poly(styrene-co-glycidyl methacrylate) (SG) copolymer were simultaneously incorporated into immiscible poly(vinylidene fluoride)/poly(l-lactic acid) (PVDF/PLLA) blends. The carboxylic acid groups of both the PMMA oligomer and PLLA can react with the epoxide groups on the SG main chains. Therefore, novel compatibilizing polymers with both PMMA and PLLA chains grafted onto the SG main chains form in situ. The grafted PMMA chains can entangle with PVDF, and the grafted PLLA chains are embedded in the PLLA phase, so the double-grafted copolymers act as effective compatibilizers for the PVDF/PLLA blends. Moreover, the effects of the PMMA molecular weight and PMMA loading (number of grafted PMMA side chains) on the compatibilization efficiency were investigated. The compatibilizing efficiency increases with increasing molecular weight and number of side chains in the ranges considered in this study. This one-pot synthesis of double-grafted compatibilizers by in situ grafting provides a new and simple method to prepare double-comb compatibilizers, and it offers the possibility of high-efficiency compatibilization.

Self-assembled nanostructures from amphiphilic globular protein–polymer hybrids

Amphiphilic globular protein–polymer hybrids, consisting of poly(methyl methacrylate) (PMMA) as hydrophobic tail and globular protein as hydrophilic head, are prepared by the end-functional PMMA covalently binding to the primary amino groups of bovine serum albumin (BSA) in the phosphate buffer saline (PBS)/acetone mixture solvents at pH 5. The self-assembly behaviors of amphiphilic BSA–PMMA hybrids are explored in aqueous solution by the dynamic light scatter (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The self-assembled morphologies of the amphiphilic BSA–PMMA hybrids are controlled by the length of hydrophobic PMMA chains. The amphiphilic BSA–PMMA hybrids with the longer hydrophobic PMMA chains self-assembled into spherical vesicles and elongated tubular vesicles, and conversely, they self-assembled into micelles. A vesicle consists of BSA as two outer hydrophilic layers and PMMA as hydrophobic wall. Amphiphilic globular protein–polymer hybrids consist of PMMA as hydrophobic tail and globular protein BSA as hydrophilic head. Amphiphilic globular protein–polymer hybrids self-assembled into micelles or vesicles in phosphate buffer saline. The self-assembled morphology of amphiphilic protein–polymer hybrids was controlled by adjusting the length of hydrophobic chains.

Viscoelastic behavior of PMMA/grafted PBA nanoparticle systems in the molten state

The viscoelastic properties of poly(methyl methacrylate) (PMMA)/grafted poly(butyl acrylate) (PBA) nanoparticle systems were investigated. The rubber particles consist of PBA core (60 nm in diameter) and grafted PMMA shell. The grafting degree, defined as the weight ratio of grafted PMMA to PBA particles, ranges from 0.8 to 1.5. Two series of samples, A series with 7.5 wt.% of PBA content and B series with 12 wt.% of PBA content, were used. The systems exhibited fast and slow relaxation process, the former reflecting the relaxation of the matrix PMMA chains and the latter being attributed to grafted PBA particles. For A series samples, time-temperature superposition (TTS) was held well over the frequency (ω) and temperature (T) ranges measured. However, for B series samples, TTS was not satisfied at low ω due to the particle-particle interaction of grafted PBA particles, although the samples obeyed TTS at high ω associated with the relaxation with entanglement of matrix PMMA. At high T and low ω region, the B series samples showed a sol-gel transition at elevating T and the critical gel behavior characterized with a power-law relationship, G′ = G″/tan(nπ/2) ∝ ωn, was observed. This behavior suggested formation of a self-similar, fractal structure of grafted PBA particles. The critical gel temperature (T gel) and the critical exponent (n) were determined for the B series samples. TEM observations revealed that as-prepared A and B samples had well-dispersed particles but the B samples after viscoelastic measurements had fragmented networks of the PBA particles, confirming that the sol-gel transition occurred for the PMMA/grafted PBA systems at elevating T.

Poly(methyl methacrylate) organoclay composites; interactions of organic modifier with the polymer effecting thermal degradation behavior

In this work, poly(methyl methacrylate), PMMA, and its composites involving montmorillonites modified with different quaternary ammonium salts were prepared and characterized by X-ray Diffraction, XRD, Transmission Electron Microscopy, TEM, Thermogravimetry, TGA and direct pyrolysis mass spectrometry, DPMS. Increase in the interlayer spacing of the silicate layers compared to the corresponding organically modified clay was detected in X-ray diffractograms for all the PMMA composites in accordance with TEM results indicating mainly intercalated structure. The thermal stability of all PMMA composites increased compared to the neat PMMA. Thermal stability of the composites increased with the increase in the interlayer spacing of the silicate layers. This behavior was directly associated with better intercalation of PMMA chains within the galleries with larger interlayer spacing of silicate layers. Direct pyrolysis mass spectrometry results pointed out reactions between amine and hydroxyl groups of organic modifiers with the ester groups of PMMA generating methanol and thermally more stable chains.

Grafting and properties of a porous poly(methyl methacrylate) film on a silicon surface by a one‐step dipping method

ABSTRACTIn this study, we prepared a porous poly(methyl methacrylate) (PMMA) film on an Si surface with a novel dipping method. We conducted the process by directly dipping the Si substrate into acidic aqueous media in a simple flask at 10 °C. First, 4‐nitrobenzene diazonium tetrafluoroborate (NBD) was spontaneously reduced at the Si surface. Then, the aryl radicals during the reduction of NBD were directly grafted onto the Si surface. Meanwhile, the aryl radicals initiated the polymerization of methyl methacrylate (MMA) monomers, and the radical‐terminated PMMA chains formed in the solution were grafted onto the Si surface. Because water was a poor solvent for MMA, the grafted PMMA chains easily aggregated together, and this resulted in a porous polymer film. The porosity of the film depended on the grafting time and the MMA concentration. Furthermore, the permittivity of the porous PMMA film was relatively low, and its dielectric dissipation factor was extremely small. Therefore, its excellent dielectric properties should allow the porous film to have many applications in industry. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44930.

Compatibilization mechanism induced by organoclay in PMMA/PS blends

In this work, the effect of adding organoclay (Cloisite 20A) to a poly(methyl metacrylate) (PMMA)/polystyrene (PS) blend was evaluated in order to understand the compatibilization mechanism taking place. The blend morphology was quantified using micrographs obtained by scanning electron microscopy and observed by transmission electron microscopy. The state of dispersion of the clay was studied using small angle X-ray scattering and wide angle X-ray scattering and by applying the Carreau-Yasuda with a yield stress model to small amplitude oscillatory shear (SAOS) data. Morphological analyses revealed that the clay was intercalated, that its addition resulted in a decrease in the size of the dispersed phase and that it was preferentially located at the interface, except in the case of saturated interfaces, in which case the remaining clay was dispersed in PMMA. By applying the simplified Palierne model to SAOS experiments, the interfacial tension between the polymers forming the blend was inferred and shown to decrease upon addition of clay. The relaxation spectra inferred from the SAOS data, using the Honerkamp and Weese method, revealed four relaxation times: Relaxation of PMMA and PS chains, relaxation of the droplet shape, as well as an additional relaxation phenomenon attributed to the Marangoni stress. Although Marangoni stresses have already been studied in the case of blends compatibilized by block copolymers, this is the first time that it has been evidenced in the case of a clay as compatibilizer.

Structural changes of PMMA substrates with different electrolyte solutions: A molecular dynamics study

The structure of polyelectrolyte substrates could be changed from swelling to collapse by exchanging different electrolyte solutions. However, few investigations explained the phenomenon at the molecular level. In this paper, we employed a molecular dynamics method to simulate the structural changes of poly(methacrylic acid sodium) (PMMA) substrates with the presence of pure water, NH4Cl, tetramethylammonium bromide (TMAB) and tetraethylammonium bromide (TEAB) solution. The simulated results show that the percentage of water molecules penetrated into the substrate and the height of PMMA substrates gradually decrease following the order pure water>NH4+>TMA+>TEA+. This may be ascribe to the hydrophobic interaction between the solute cations and water molecules, which can exclude water molecules from the substrates and further influence the height of PMMA substrates. In particular, through the observation at the molecular level, it is obvious that the existence of water bridge structure and salt bridge structure formed between penetrated particles and PMMA chains play a key role in the structural change of PMMA substrates. Water bridges can induce the swelling of PMMA substrates and salt bridges will result in collapse happening. This work may promote a further understanding of the cationic effects on the structure of PMMA substrates at the molecular level and provide a new insight to study the interfacial micro-structure of other biological substrates in future.

Reduction of Line Edge Roughness of Polystyrene-block-Poly(methyl methacrylate) Copolymer Nanopatterns By Introducing Hydrogen Bonding at the Junction Point of Two Block Chains.

To apply well-defined block copolymer nanopatterns to next-generation lithography or high-density storage devices, small line edge roughness (LER) of nanopatterns should be realized. Although polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) has been widely used to fabricate nanopatterns because of easy perpendicular orientation of the block copolymer nanodomains and effective removal of PMMA block by dry etching, the fabricated nanopatterns show poorer line edge roughness (LER) due to relatively small Flory-Huggins interaction parameter (χ) between PS and PMMA chains. Here, we synthesized PS-b-PMMA with urea (U) and N-(4-aminomethyl-benzyl)-4-hydroxymethyl-benzamide (BA) moieties at junction of PS and PMMA chains (PS-U-BA-PMMA) to improve the LER. The U-BA moieties serves as favorable interaction (hydrogen bonding) sites. The LER of PS line patterns obtained from PS-U-BA-PMMA was reduced ∼25% compared with that obtained from neat PS-b-PMMA without BA and U moieties. This is attributed to narrower interfacial width induced by hydrogen bonding between two blocks, which is confirmed by small-angle X-ray scattering. This result implies that the introduction of hydrogen bonding into block copolymer interfaces offers an opportunity to fabricate well-defined nanopatterns with improved LER by block copolymer self-assembly, which could be a promising alternative to next-generation extreme ultraviolet lithography.

Molecular confinement of solid and gaseous phases of self-standing bulk nanoporous polymers inducing enhanced and unexpected physical properties

In this work it is provided the first evidence of the polymer chains confinement within self-standing pore walls of nanoporous materials based on poly (methyl methacrylate) (PMMA). This was made possible by producing a series of porous samples with a wide range of pore sizes between 90 nm and 3 μm using processes combining CO2 sorption, selective block copolymer swelling or homogeneous physical foaming. Mobility restrictions of the PMMA chains in the porous samples with pore size below 200 nm was consistently demonstrated with several experimental techniques, including differential scanning calorimetry, Raman spectroscopy, and broadband dielectric spectroscopy.In addition, several scale-reduction phenomena related to the constitutive elements of the porous materials, both in the polymeric and gaseous phases, and to the porous architecture are identified. The significance of these phenomena on macroscopic electrical conductivity and permittivity of the nanoporous materials is demonstrated, and the presented observations support previous explanations of improved mechanical properties and thermal insulation of this type of nano-materials.