Solid-State Reaction of Alkylamines with CO in Ambient Air.

This paper explores possible procedures to accelerate CO capture from ambient air by a crystalline alkylamine surfactant (octadecylamine), leading to the corresponding crystalline ammonium-carbamate. Conversion of the amine to the carbamate, in different conditions, is studied by four different techniques: WAXD, FTIR, TGA, and DSC. The WAXD study also gives relevant information on the crystal structures of both amine and derived carbamate.

Salicylic Acid Release from Syndiotactic Polystyrene Staple Fibers.

Films and fibers of syndiotactic polystyrene (sPS), being amorphous or exhibiting nanoporous crystalline (NC) or dense crystalline phases, were loaded with salicylic acid (SA), a relevant non-volatile antimicrobial molecule. In the first section of the paper, sPS/SA co-crystalline (CC) δ form is characterized, mainly by wide angle X-ray diffraction (WAXD) patterns and polarized Fourier transform infrared (FTIR) spectra. The formation of sPS/SA δ CC phases allows the preparation of sPS fibers even with a high content of the antibacterial guest, which is also retained after repeated washing procedures at 65 °C.

Hydrogen Bonded Dimer of an Alcohol with the Derived Carboxylic Acid Triggering their Sorption by Nanoporous-crystalline PPO Films.

Films exhibiting nanoporous-crystalline (NC) phases of poly(2,6-dimethyl-1,4-phenylene) oxide (PPO), which are highly effective to absorb apolar organic guest molecules, are also able to absorb polar molecules (like alcohols and carboxylic acids) but only from concentrated organic solutions. NC PPO films, which do not absorb alcohols and carboxylic acids from diluted aqueous solutions, exhibits a huge uptake (even above 30 wt %) of benzyl alcohol (BAL) and benzoic acid (BA), if BA is obtained by spontaneous room temperature oxidation of BAL in aqueous solution. This phenomenon is rationalized by an easy uptake, mainly by the PPO intrahelical crystalline empty channels, of a BAL/BA 1/1 hydrogen-bonded dimer.

Segregation of Benzoic Acid in Polymer Crystalline Cavities.

Benzoic acid (BA) and its derivatives are very attractive because of their pharmacological properties, such as antioxidant, radical-regulating, antiviral, antitumor, anti-inflammatory, antimicrobial and antifungal. Syndiotactic polystyrene (sPS) and poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) films exhibiting co-crystalline phases with BA were prepared and characterized by WAXD, FTIR and polarized FTIR measurements. The FTIR measurements clearly showed that BA was present mainly as a dimer in the crystalline channels of the ε form of sPS as well as in the α form of PPO, as generally occurs not only in the solid state but also in organic dilute solutions.

Molecular Features Behind Formation of α or β Co-Crystalline and Nanoporous-Crystalline Phases of PPO.

Guest molecular features determining the formation of α and β phases of poly(2-6-dimethyl-1,4-phenylene) oxide (PPO) are explored by collecting literature data and adding many new film preparations, both by solution casting and by guest sorption in amorphous films. Independently of the considered preparation method, the α-form is favored by the hydrophobic and bulky guest molecules, while the hydrophilic and small guest molecules favor the β-form. Furthermore, molecular modeling studies indicate that the β-form inducer guests establish stronger dispersive interactions with the PPO units than the α-form inducer guests.

Dependence on Film Thickness of Guest-Induced Perpendicular Orientation in PPO Films.

For poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) films exhibiting nanoporous-crystalline (NC) phases, orientation (i.e., crystalline polymer chain axes being preferentially perpendicular to the film plane) is obtained by crystallization of amorphous films, as induced by sorption of suitable low-molecular-mass guest molecules.

Monomeric and Dimeric Carboxylic Acid in Crystalline Cavities and Channels of Delta and Epsilon Forms of Syndiotactic Polystyrene.

Delta (δ) and epsilon (ε) co-crystalline forms of syndiotactic polystyrene with a carboxylic acid guest were obtained by sorption of liquid hexanoic acid in syndiotactic polystyrene films exhibiting delta and epsilon nanoporous-crystalline forms. The characterization study is facilitated by axially stretched syndiotactic polystyrene films, used both for polarized FTIR spectra and for WAXD fiber patterns. Particularly informative are two carbonyl-stretching FTIR peaks, attributed to monomeric and dimeric hexanoic acid.

c-Perpendicular Orientation of Poly(ʟ-lactide) Films.

Poly(ʟ-lactide) (PLLA) films, even of high thickness, exhibiting co-crystalline and crystalline α phases with their chain axes preferentially perpendicular to the film plane (c orientation) have been obtained. This c orientation, unprecedented for PLLA films, can be achieved by the crystallization of amorphous films as induced by low-temperature sorption of molecules being suitable as guests of PLLA co-crystalline forms, such as ,-dimethylformamide, cyclopentanone or 1,3-dioxolane. This kind of orientation is shown and quantified by two-dimensional wide-angle X-ray diffraction (2D-WAXD) patterns, as taken with the X-ray beam parallel to the film plane (EDGE patterns), which present all the hk0 arcs centered on the meridian.

Nanoporous Crystalline Composite Aerogels with Reduced Graphene Oxide.

High-porosity monolithic composite aerogels of syndiotactic polystyrene (sPS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) containing reduced graphene oxide (r-GO) were prepared and characterized. The composite aerogels obtained by supercritical carbon dioxide (scCO) extraction of sPS/r-GO and PPO/r-GO gels were characterized by a fibrillar morphology, which ensured good handling properties. The polymer nanoporous crystalline phases obtained within the aerogels led to high surface areas with values up to 440 m g.

Axial Orientation of Co-Crystalline Phases of Poly(2,6-Dimethyl-1,4-Phenylene)Oxide Films.

Films exhibiting co-crystalline (CC) phases between a polymer host and low-molecular-mass guest molecules are relevant for many applications. As is usual for semi-crystalline polymers, axially oriented films can give relevant information on the crystalline structure, both by Wide Angle X-ray diffraction fiber patterns and by polarized Fourier-transform infrared spectroscopy. Axially oriented CC phases of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) with 1,3,5-trimethylbenzene (mesitylene) can be simply obtained by the stretching of CC PPO films.

Intercalation compounds of a smectite clay with an ammonium salt biocide and their possible use for conservation of cultural heritage.

Ordered intercalation compounds between a smectite mineral clay (montmorillonite, Mt) and the ammonium salt mainly used for stone material disinfection procedures (i.e. N-Alkyl-N-benzyl-N,N-dimethylammonium chloride, shortly known as benzalkonium chloride, BAC), leading to an increase of interlayer distance from 1.

Graphene Oxide and Oxidized Carbon Black as Catalyst for Crosslinking of Phenolic Resins.

Influence of different graphite-based nanofillers on crosslinking reaction of resorcinol, as induced by hexa(methoxymethyl)melamine, is studied. Curing reactions leading from low molecular mass compounds to crosslinked insoluble networks are studied by indirect methods based on Differential Scanning Calorimetry. Reported results show a catalytic activity of graphene oxide (eGO) on this reaction, comparable to that one already described in the literature for curing of benzoxazine.

Catalytic Activity of Oxidized Carbon Waste Ashes for the Crosslinking of Epoxy Resins.

In this study, two different fillers were prepared from carbon-based ashes, produced from the wooden biomass of a pyro-gasification plant, and starting from lignocellulosic waste. The first type was obtained by dry ball-milling (DBA), while the second one was prepared by oxidation in HO of the dry ball-milled ashes (oDBA). The characterization of the fillers included wide-angle x-ray diffraction (WAXD), thermogravimetric, and Fourier-transform infrared spectroscopy (FTIR) analysis.

Release of Cationic Drugs from Charcoal.

The goal of this research is to improve preparation of charcoal adducts in a manner suitable for cationic drug release, possibly using an eco-friendly procedure. Charcoal, widely commercialized for human ingestion, is oxidized by hydrogen peroxide in mild conditions. Adducts of a cationic drug (lidocaine hydrochloride, a medication used as local anesthetic) with charcoal are prepared after basification of charcoal and characterized mainly by elemental analysis, wide-angle X-ray diffraction, infrared spectroscopy and thermogravimetry.

Edge-Oxidation of Graphites by Hydrogen Peroxide.

A simple and eco-friendly procedure of edge oxidation of high-surface area graphites, based on hydrogen peroxide treatments at 60 °C, is presented. Already, short-term treatments lead to O/C weight ratios higher than 0.1, leaving unaltered interlayer spacing and correlation length.

PLA Melt Stabilization by High-Surface-Area Graphite and Carbon Black.

Small amounts of carbon nanofillers, specifically high-surface-area graphite (HSAG) and more effectively carbon black (CB), are able to solve the well-known problem of degradation (molecular weight reduction) during melt processing, for the most relevant biodegradable polymer, namely poly(lactic acid), PLA. This behavior is shown by rheological measurements (melt viscosity during extrusion experiments and time sweep-complex viscosity) combined with gel permeation chromatography (GPC) experiments. PLA's molecular weight, which is heavily reduced during melt extrusion of the neat polymer, can remain essentially unaltered by simple compounding with only 0.

Oxidized Carbon Black as an Activator of Transesterification Reactions under Solvent-Free Conditions.

A metal-free procedure for oxidation of carbon black (CB), under mild and ecofriendly conditions, is described. The procedure, based on 5/1 w/w HO/HSO, when applied to high-surface-area CB, leads to oxidation contents (O/C = 0.66) comparable to those obtained for graphite with the more aggressive and metal-based Hummers method (O/C 0.

Green and Facile Esterification Procedure Leading to Crystalline-Functionalized Graphite Oxide.

A simple and eco-friendly procedure of esterification of graphite oxide (GO), which uses acetic anhydride as a model reagent and ethyl acetate as a green solvent, is reported. The procedure leads to high functionalization degrees (at least up to 4.5 mol % of acetyl groups, referred to as graphitic C atoms) and it is much more effective than the literature method based on pure acetic anhydride.

Catalytic Activity of Oxidized Carbon Black and Graphene Oxide for the Crosslinking of Epoxy Resins.

This article compares the catalytic activities of oxidized carbon black (oCB) and graphene oxide (eGO) samples on the kinetics of a reaction of diglycidyl ether of bisphenol A (DGEBA) with a diamine, leading to crosslinked insoluble networks. The study is mainly conducted by rheometry and Differential Scanning Calorimetry (DSC). Following the same oxidation procedure, CB samples are more efficiently oxidized than graphite samples.

Label-Free Vapor Selectivity in Poly(p-Phenylene Oxide) Photonic Crystal Sensors.

The lack of sensors for low cost, extensive, and continuous detection of vapor pollutants is a serious concern for health and safety in industrialized urban areas. Colorimetric sensors, such as distributed Bragg reflectors made of polymers, could achieve this task thanks to their low cost and easy signal transduction but are typically affected by low vapor permeability and lack of selectivity without chemical labeling. Here we demonstrate all-polymer Bragg multilayers for label-free selective detection of organic volatile compounds.

Intense Chiral Optical Phenomena in Racemic Polymers by Cocrystallization With Chiral Guest Molecules: A Brief Overview.

This review is devoted to the chiral optical behavior of films of racemic polymers whose chirality is induced by cocrystallization with nonracemic (also temporary) guest molecules. We provide examples of macromolecular amplification of chirality, produced by molecular and supramolecular mechanisms, on industrially relevant polymers like poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) and syndiotactic polystyrene (s-PS).

Monolithic polymeric aerogels with VOCs sorbent nanoporous crystalline and water sorbent amorphous phases.

Monolithic syndiotactic polystyrene (s-PS) aerogels, formed by highly crystalline nanofibrils with a hydrophobic nanoporous-crystalline phase and a hydrophilic amorphous phase have been prepared and characterized. These aerogels, with a high degree of sulfonation of the amorphous phase and nearly negligible sulfonation of the crystalline phase, are obtained by treating physical gels exhibiting δ-clathrate form. With respect to unsulfonated nanoporous-crystalline polymeric aerogels, these new selectively sulfonated aerogels present the great advantage of a high water diffusivity and water uptake up to 600 wt %.

Regio- and enantioselective friedel-crafts reactions of indoles to epoxides catalyzed by graphene oxide: a green approach.

Graphene oxide efficiently promotes high regio- and enantioselective ring opening reactions of aromatic epoxides by indoles addition, in solvent- and metal-free conditions. The Friedel-Crafts products were obtained with enantioselectivity up to 99 % ee. The complete inversion of stereochemistry indicates the occurrence of SN 2-type reaction, which assures high level of enantioselectivity.

Enantiomeric guests with the same signs of chiral optical responses.

The circular dichroism of non-racemic molecules, being guests of co-crystalline phases of s-PS films, has been studied. Unexpectedly, the chiral response of non-racemic guest molecules does not depend on their R or S molecular chirality but essentially only on the polymer host supramolecular chirality.

Monolithic nanoporous crystalline aerogels.

Monolithic aerogels can be easily obtained by drying physical gels formed by linear uncross-linked polymers. Preparation methods, structure, and properties of these physically cross-linked polymeric aerogels are reviewed, with particular emphasis to those whose cross-linking knots are crystallites and, more in particular, crystallites exhibiting nanoporous-crystalline forms. The latter aerogels present beside disordered amorphous micropores (typical of all aerogels) also all identical nanopores of the crystalline phases.