Combinatorial generation and replication-directed assembly of complex and varied geometries with thin films of diblock copolymers

Directed assembly of fine-scale, very complex patterns with a variety of features, including terminations, jogs, disclinations, acute and obtuse bends, and sharp radii of curvature, was achieved with a symmetric poly(styrene-block-methylmethacrylate) (PS-b-PMMA) copolymer. The complex pattern was generated spontaneously by spin coating and annealing a thin film of a lamellae-forming block copolymer on a chemically neutral surface. The resulting "fingerprint" pattern had a domain spacing of 47.5 nm. Oxygen plasma treatment of the block copolymer converted it into an insoluble chemical nanopattern that was quantified by XPS, goniometry, and the wetting behavior of the block copolymer. Spin coating a second thin film of the block copolymer and annealing resulted in directed assembly that replicated the fingerprint pattern, including the most complicated defect structures. A computer vision algorithm was developed and implemented to compare the patterns quantitatively, taking into account inherent differences in image contrast, scale, rotation, and translation.     

Synthesis and characterization of new soluble aromatic polyamides derived from 1,4‐Bis(4‐carboxyphenoxy)‐2, 5‐di‐tert‐butylbenzene

Aromatic polyamides based on a novel bis(ether‐carboxylic acid) were synthesized by the direct phosphorylation condensation method. 1,4‐Bis(4‐carboxyphenoxy)‐2,5‐di‐tert‐butylbenzene was combined with various diamines containing flexible linkages and side substituents to render a set of eight novel aromatic polyamides. The polymers were produced with high yields and moderate to high inherent viscosities (0.49–1.32 dL/g) that corresponded to weight‐average and number‐average molecular weights (by gel permeation chromatography) of 31,000–80,000 and 19,000–50,000, respectively. Except for a single example, the polyamides were essentially amorphous and soluble in a variety of common solvents such as cyclohexanone, dioxane, and tetrahydrofuran. They showed glass‐transition temperatures of 250–295 °C (by differential scanning calorimetry) and 10% weight loss temperatures above 460 °C, as revealed by thermogravimetric analysis in nitrogen. Polymer films, obtained by casting from N,N‐dimethylacetamide solutions, exhibited good mechanical properties, with tensile strengths of 83–111 MPa and tensile moduli of 2.0–2.2 GPa. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 475–485, 2001     

Aromatic polyamides and polyimides derived from 3,3′-diaminobiphenyl: Synthesis,characterization, and molecular simulation study

In this article a new synthesis of 3,3′-diaminobiphenyl (3,3′-DABP) is described, along with the preparation and characterization of polyamides and polyimides based on it. Reactivity of this monomer was calculated by a molecular simulation study, using ab initio quantum-mechanical methods. Terephthaloyl and isophthaloyl chloride were used for the synthesis of polyamides, while 3,3′,4,4′-biphenylenetetracarboxylic acid dianhydride and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride were used for the synthesis of polyimides. Medium to high molecular weight polymers were attained, with inherent viscosities near or higher than 1.0 dL/g, the solubility of the 3,3′-DABP polymers was much better than that of the homologous polymers from benzidine (4,4′-DABP), the glass-transition temperatures were lower, by about 40°C, and the thermal resistance, as measured by thermogravimetry, was virtually the same. Amorphous films, made from cast polymer solutions, showed excellent mechanical properties, comparable to conventional aromatic polyamides and polyimides. Theoretical calculations demonstrated that the radius of giration, end-to-end distance and density of poly(3,3′-DABP-isophthalamide) were lower than those of poly(4,4′-DABP-isophthalamide), as a consequence of the chain folding induced in the backbone by the m-substitution in 3,3′-DABP. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4646–4655, 1999     

Novel polyimides with p-nitrophenyl pendant groups. Synthesis and characterization

Polyimides derived from a new dianhydride with p-nitrophenyl pendant groups have been synthesized and their properties compared with those of a reference series, without side groups. The polymers were obtained by combination of the novel monomer with aromatic diamines, in a two-step procedure that involved the synthesis of poly(amic acid) or poly(amic silyl ester) intermediates and the cyclization of them to polyimides by thermal treatment. The introduction of the polar nitro groups caused significant increase of the T_gs. On the contrary, the thermal stability was reduced because of the breakdown of C_Ar—NO₂ linkages around 400^oC. A slight decrease in mechanical properties was observed, due to the bulkiness of the side groups, that also produced an important decrease in the strength of the β relaxation, as determined by dynamic mechanical analysis. The solubility of the current polyimides in organic solvents was as poor as that of the parent unsubstituted polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3377–3384, 1999     

Fracture behavior–morphology relationships in an unsaturated polyester resin modified with a liquid oligomer

An unsaturated polyester (UP) resin modified with a liquid polymer, polyoxypropylenetriamine (POPTA), at a concentration of 10 wt% has been precured at several temperatures. Phase separation takes place before gelation at all precure temperatures used. The glass‐transition region has been analyzed by dynamic mechanical analysis. Mechanical properties have been related to microstructural features. With a precure temperature fixed, the unsaturated polyester (UP) resin has also been modified with different contents of POPTA. Fracture toughness of the mixtures has also been analyzed and results are compared to those for the unmodified mixture. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1677–1685, 1999     

Synthesis and characterization of novel polyimides with bulky pendant groups

New dianhydrides containing t‐butyl and phenyl pendant groups have been synthesized and used as monomers, together with commercial diamines, to prepare novel polyimides. The influence of the chemical structure of the monomers on their reactivity has been studied by quantum semiempirical methods. The polyimides have been characterized by FTIR and by NMR in the case of soluble polymers. The presence of pendant groups and the method used to imidize polyimide precursors greatly affected polymer properties such as solubility, glass transition temperature, thermal stability, and mechanical properties. As a rule, the novel polyimides showed better solubility in organic solvents than the parent polyimides. Glass transition temperatures in the range 250–270°C and decomposition temperatures over 520°C were observed for the set of current polymers. Tensile strengths up to 135 MPa and mechanical moduli up to 3.0 GPa were measured on films of the current polyimides. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 805–814, 1999     

Mesoporous materials incorporating a zinc(II) complex: Synthesis and direct luminescence quantum yield determination

New luminescent inorganic–organic hybrid materials incorporating the luminescent zinc(II) complex ZnL₂ (λ_em = 457 nm and Φ_em = 4.4% reference values for ZnL₂; HL = chelating ligand resulting from the reaction between salicylaldehyde and 3-aminopropyltriethoxysilane), covalently bonded to different types of mesoporous silica hosts (namely MCM-41, MCM-48 and SBA-15), were prepared via both the methods of grafting post-synthesis (GPS) and one-pot synthesis (OPS). The products obtained, which form the GPS [(GPS)(Zn/MCM-41), (GPS)(Zn/MCM-48), (GPS)(Zn/SBA-15)] and the OPS [(OPS)(Zn/MCM-41), (OPS)(Zn/MCM-48), (OPS)(Zn/SBA-15)] series, contain the ZnL₂ guest covalently bonded to the silica framework through silicon–oxygen bonds formed when the silane group is placed at the periphery of the Zn(II) coordination sphere. GPS and OPS materials were characterized by powder X-ray diffraction, N₂ adsorption/desorption, thermogravimetric analysis (TGA) and UV/vis spectroscopy. For the new mesoporous materials the emission quantum yield (EQY) was measured by means of an integrating sphere combined with a spectrofluorimeter. The ZnL₂ loading (measured by the ZnL₂/SiO₂ ratio calculated from TGA data) for MCM-41 appears to be independent of the synthesis procedure, whereas, for both MCM-48 and SBA-15, the ZnL₂/SiO₂ ratio of the materials obtained via OPS is about four times higher than products obtained from GPS. The ZnL₂ loaded GPS and OPS series show λ_em maxima at about 485 and 455 nm, respectively. Moreover, with reference to EQY (GPS)(Zn/SBA-15) and (OPS)(Zn/SBA-15), although featuring ZnL₂/SiO₂ ratios of 0.13 and 0.45, respectively, they showed similar EQY values: 2% and 5%. On the contrary, (GPS)(Zn/MCM-41) and (OPS)(Zn/MCM-41) which give similar ZnL₂/SiO₂ ratios (0.09 and 0.14) exhibit very different EQY, i.e. 2% and 22%, respectively.     

Seriniquinones as Therapeutic Leads for Treatment of BRAF and NRAS Mutant Melanomas

Isolated from the marine bacteria Serinicoccus sp., seriniquinone (SQ1) has been characterized by its selective activity in melanoma cell lines marked by its modulation of human dermcidin and induction of autophagy and apoptosis. While an active lead, the lack of solubility of SQ1 in both organic and aqueous media has complicated its preclinical evaluation. In response, our team turned its effort to explore analogues with the goal of returning synthetically accessible materials with comparable selectivity and activity. The analogue SQ2 showed improved solubility and reached a 30–40-fold greater selectivity for melanoma cells. Here, we report a detailed comparison of the activity of SQ1 and SQ2 in SK-MEL-28 and SK-MEL-147 cell lines, carrying the top melanoma-associated mutations, BRAF^V600E and NRAS^Q61R, respectively. These studies provide a definitive report on the activity, viability, clonogenicity, dermcidin expression, autophagy, and apoptosis induction following exposure to SQ1 or SQ2. Overall, these studies showed that SQ1 and SQ2 demonstrated comparable activity and modulation of dermcidin expression. These studies are further supported through the evaluation of a panel of basal expression of key-genes related to autophagy and apoptosis, providing further insight into the role of these mutations. To explore this rather as a survival or death mechanism, autophagy inhibition sensibilized BRAF mutants to SQ1 and SQ2, whereas the opposite happened to NRAS mutants. These data suggest that the seriniquinones remain active, independently of the melanoma mutation, and suggest the future combination of their application with inhibitors of autophagy to treat BRAF-mutated tumors.     

The role of additives in the recycling of polymers

The main problems in post-consumer plastics recycling are due to the degradation undergone by the polymers during processing steps and by the products during their lifetime and, for heterogeneous recycling, to the incompatibility of different polymers. To reduce the negative effects of the recycling steps, two main ways can be adopted for homogeneous materials: restabilization during the recycling to avoid or at least to slow the degradation and addition of fillers and modifiers capable of improving the performance of thermoplastic polymers without increasing the final cost of the secondary material. In the case of mixed plastics, compatibilization is the necessary step to obtain secondary materials with acceptable properties.