Phosphine functionalized polyaniline nanostructures

We study the problem of limited functionalization options for polyaniline through the surface attachment of phosphine coupling reagents. These studied linkers are P(CH₂OH)₃ and Ph₂PCH₂OH, and are attached to both conventional and nanostructured polyaniline. Additionally, model compounds are considered, extending the scope of our analysis. The successful attachment results indicate the potential for further functionalization, using the hydroxymethyl terminal groups of the phosphines for primary and secondary amine chemistry. These results should enable the development of sensitive and molecule-specific polyaniline-based devices

Polysaccharide compositions of collenchyma cell walls from celery (Apium graveolens L.) petioles

Abstract Background Collenchyma serves as a mechanical support tissue for many herbaceous plants. Previous work based on solid-state NMR and immunomicroscopy suggested collenchyma cell walls (CWs) may have similar polysaccharide compositions to those commonly found in eudicotyledon parenchyma walls, but no detailed chemical analysis was available. In this study, compositions and structures of cell wall polysaccharides of peripheral collenchyma from celery petioles were investigated. Results This is the first detailed investigation of the cell wall composition of collenchyma from any plant. Celery petioles were found to elongate throughout their length during early growth, but as they matured elongation was increasingly confined to the upper region, until elongation ceased. Mature, fully elongated, petioles were divided into three equal segments, upper, middle and lower, and peripheral collenchyma strands isolated from each. Cell walls (CWs) were prepared from the strands, which also yielded a HEPES buffer soluble fraction. The CWs were sequentially extracted with CDTA, Na2CO3, 1 M KOH and 4 M KOH. Monosaccharide compositions of the CWs showed that pectin was the most abundant polysaccharide [with homogalacturonan (HG) more abundant than rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II)], followed by cellulose, and other polysaccharides, mainly xyloglucans, with smaller amounts of heteroxylans and heteromannans. CWs from different segments had similar compositions, but those from the upper segments had slightly more pectin than those from the lower two segments. Further, the pectin in the CWs of the upper segment had a higher degree of methyl esterification than the other segments. In addition to the anticipated water-soluble pectins, the HEPES-soluble fractions surprisingly contained large amounts of heteroxylans. The CDTA and Na2CO3 fractions were rich in HG and RG-I, the 1 M KOH fraction had abundant heteroxylans, the 4 M KOH fraction was rich in xyloglucan and heteromannans, and cellulose was predominant in the final residue. The structures of the xyloglucans, heteroxylans and heteromannans were deduced from the linkage analysis and were similar to those present in most eudicotyledon parenchyma CWs. Cross polarization with magic angle spinning (CP/MAS) NMR spectroscopy showed no apparent difference in the rigid and semi-rigid polysaccharides in the CWs of the three segments. Single-pulse excitation with magic-angle spinning (SPE/MAS) NMR spectroscopy, which detects highly mobile polysaccharides, showed the presence of arabinan, the detailed structure of which varied among the cell walls from the three segments. Conclusions Celery collenchyma CWs have similar polysaccharide compositions to most eudicotyledon parenchyma CWs. However, celery collenchyma CWs have much higher XG content than celery parenchyma CWs. The degree of methyl esterification of pectin and the structures of the arabinan side chains of RG-I show some variation in the collenchyma CWs from the different segments. Unexpectedly, the HEPES-soluble fraction contained a large amount of heteroxylans

Synchrotron X-ray scattering reveals early-stage crystallinity during the self-assembly of polyaniline nanotubes with rectangular cross-sections

The use of synchrotron X-ray diffraction to study the crystallographic structure of nanostructure polyaniline is reported. It is shown to reveal unprecedented crystallographic information, particularly for early-stage self-assembled intermediate structures that are critical to the formation process. We discuss the new peaks, which are enabled here by specific advantages of synchrotron X-rays, including higher resolution diffraction patterns, and lower sample quantity requirements. The findings have application to the study of the structural evolution underpinning PANI nanotube formation.Web of Science16123-242742273

Enhanced Microwave Synthesis: Fine-Tuning of Polyaniline Polymerization

A series of energy- and time-efficient enhanced microwave syntheses (EMS) of polyaniline (PANI) have been performed and are discussed herein. The syntheses were performed at different microwave power levels while keeping the reaction system at a constant temperature of 24 ± 1 °C, with the samples extracted after 10 min of reaction. Molecular weights were determined with GPC (gel permeation chromatography) and showed that the molecular weight of the microwave-generated materials depends on applied power: the higher the power level, the greater the molecular weight. The chemical structure was investigated by FTIR and UV–vis spectroscopy, while the morphology was imaged using scanning electron microscopy (SEM). FTIR and UV–vis spectroscopy confirmed the formation of PANI, and SEM indicated the presence of a mixed morphology, with a prevalence of nanofibers with different aspect ratios. The conductivity of the samples (ca. 3–3.5 S cm^–1) was found to be relatively independent of microwave power levels. Surface area measurements were carried out using Brunauer–Emmett–Teller (BET) method, with samples synthesized using EMS showing higher surface areas when compared with conventionally synthesized PANI. The fact that molecular weight depends on applied power implies that microwave-enhanced synthesis can be used to fine-tune PANI reaction conditions, directing it toward specific properties

Characterization of metallurgical-grade aluminas and their precursors by (27)AI NMR and XRD1

The structure of metallurgical- or smelter-grade aluminas (MGAs) is complex and poorly understood. Ultrahigh-field solid-state Al-27 NMR results on industrial as well as on laboratory-prepared aluminas are discussed in relation to XRD results. It is demonstrated that high-field NMR can effectively be used to quantify the proportion of the thermodynamically stable alpha-alumina phase in these materials. The results demonstrate that Al-27 NMR is a vital adjunct to XRD methods to quantify the transition alumina phases that invariably dominate the MGAs. The nature of the disorder in these materials, determined by Al-27 NMR, is also compared with literature data, such as XANES and EXAFS studies, on typical laboratory-prepared materials. The Utility of Al-27 NMR studies to provide new insight into the structural complexity of metallurgical aluminas is shown