Current Organic Chemistry - Volume 17, Issue 9, 2013

Cold-plasma-assisted treatment of additive-free hand sheet paper samples with styrene (ST), para-fluorostyrene (FST), parafluoro- α-methylstyrene (FMST), para-chloro-α-methylstyrene (ClMST) and para-bromo-styrene (BrST) was studied and it was established that eficiente grafting had occurred, using elemental analysis, contact angle measurement, and X-ray Photoelectron Spectroscopy (XPS). The contact angle value of a drop of water deposited at the surface of paper increased from 40° for unmodified substrate to 109, 99, 106, 100 and 107°, for ST-, FST- FMST-, ClMST- and BrST-treated samples, respectively, indicating that the surface was rendered totally hydrophobic. The treated surfaces became totally non polar, with the polar component of the surface energy decreasing from 25 mJ/m2, for pristine samples, to practically zero for the treated samples. The XPS spectra showed that the modification induced a significant decrease in the O/C ratio, as well as an increase in the intensity of the aliphatic carbon contribution to the C1s signal. Moreover, the presence of fluorine and chlorine atoms was also detected in the low resolution wide scan XPS spectra.

The purpose of this highlight is to demonstrate the importance of the surface functionalization of nanoparticles toward the design of high-tech (nano)materials. These (nano)materials are “nano-tools” for the already established interdisciplinary research fields of nanoscience and nanotechnology, which find an enormous variety of applications in different areas. In many cases, the particle-forming material, shape, and size determine the applicability of the desired nanoparticle. Nevertheless, in most of the cases other parameters must also be accurately adjusted to transform those nano-objects into functional nanoparticles, such as dispersibility, stability, reactivity, ability to recognize (or to be recognized by) other systems, and the interaction between these parameters and a matrix or dispersing medium. Most of these parameters are mainly depending on the surface characteristics of the nanoparticles. Thus, this highlight focuses not only on the importance of the surface functionalization of the nanoparticles to render them applicable, but also on the different strategies to design and obtain surface-functionalized nanoparticles (SF-NPs) and on their successful exploitation in materials science, formulation of organic–inorganic hybrid nanostructures and bio-applications.

This review highlights very recent attempts to incorporate natural renewable resources in benzoxazine resin synthesis and the properties of polybenzoxazines derived from them. Strong environmental incentives to reduce consumption of petroleum and its derivatives have also influenced the choice of raw materials for benzoxazine synthesis among many other synthetic polymer precursors. It will be seen that properties of naturally derived polybenzoxazines offer comparable physical and mechanical properties, or unique properties derived from multifunctionality of natural raw materials, often derived from multi-functionality of the natural raw materials. Benzoxazine chemistry’s versatile molecular design flexibility allows incorporation of naturally occurring phenolics, primary amines and hydroxyl compounds, such as cashew nut shell oil, urushiol, terepene, levulinic acid, and cellulose. Use of glycerol as biodiesel production waste from primary waste, such as used cooking oil and fat, as well as naturally occurring amine compound in a biomimetic manner are also discussed.

Aromatic belts are hoop-shaped, π-conjugated macrocycles that form the fundamental annular segments of single-walled carbon nanotubes (SWCNTs). Syntheses of carbon nanobelts have been challenging the chemical community for several decades. The main reason probably is the possibility that their preparation could open the way to a rational chemical synthesis carbon nanotubes. Here, we reported a successful synthesis of a belt-shaped carbon nanoring, namely cyclic [6]dianthryltetraphenylacetylene ([6]CAPA), including two anthraacetylene and four phenylacetylene units. It was prepared in a six-step synthesis via cyclic [6]dianthryltetraphenylethylene ([6]CAPE),with[36]annulene periphery.

An overview of the recent advances of functionalized poly(caprolactone)s (PCL) and their role in micellar drug delivery systems is presented. Various strategies for the functionalization of ε-caprolactone (εCL) and poly(caprolactone)s are discussed together with the approaches for the engineering of PCL-based micellar assemblies. Hydrophilic moieties, halogens, amines, and unsaturated functional groups have been conjugated to PCL by post-polymerization chemical modification. These pendant functional groups were further modified by deprotection, elimination, 1,3-Huisgen cycloaddition, or cross-linking reactions. Alternately, the anionic activation of PCL enabled the post-polymerization grafting of functional groups onto the polyester backbone. Furthermore, special attention has been given to the engineering of micellar cores to enhance their stability and interaction with encapsulated or covalently conjugated drug molecules. The engineering of the micelle hydrophilic block was also explored to achieve active targeting and enhanced cellular uptake. A combination of these strategies enabled the fine-tuning of functionalized PCL copolymers to generate micelles with properties conducive to drug delivery applications. Functionalized PCL represent a promising direction in the development of tunable micellar drug delivery systems.

A family of Newkome-type dendritic molecules bearing a disulfide anchor group, different peripheral groups (-COOtBu or - COOH) and sizes or generations (Gn=0-2) was synthesized and used as ligand for the synthesis of gold nanoparticle-cored dendrimers (NCDs). These hybrid materials were characterized by means of UV-vis spectroscopy, TEM, and IR and NMR spectroscopies, finding that the capping molecules of the organic shell determine the solubility and stability of the different NCDs, as well as the characteristics of the inorganic core through a dendritic control characteristic for Newkome-type ligands. Remarkably, a combination of detailed IR and NMR studies allows for studying the ligand-ligand and ligand-core interactions that take place in these materials. It is demonstrated that concepts, techniques and methods normally used in organic and dendritic chemistry, such as the synthesis of precisely controlled architectures and their rigorous spectroscopic characterization, can be efficiently applied to engineer novel organic-inorganic hybrid materials with enhanced properties.

Graphene oxide (GO) has been long-considered the most convenient route towards the large scale production of graphene. Additionally, the functional groups present within GO permit both covalent and non-covalent chemical functionalization, in particular with polymeric materials. The functionalization of GO therefore enables the development of graphene-based composite materials which possess the properties of both the matrix and the remarkable electrical, thermal and mechanical properties of both GO and graphene. In this review, we discuss the functionalization of GO in two broad settings: macromolecular functionalization of GO, and the use of GO in dispersed/colloidal systems. We review numerous methods for the functionalization of GO with initiators or chain transfer agents to permit controlled/living radical polymerization (CLRP) to take place from the surface of GO; the use of GO as a polymerization initiator, as well as non-covalent polymeric modification is discussed. For applications of GO in dispersed systems, we discuss the incorporation of GO into miniemulsions, emulsions and other dispersed phase polymerization systems, as well as techniques such as layer-by-layer assembly and colloidal templating. The use of GO as a ‘colloidal surfactant’ is also reviewed. These functionalization methods are discussed within the framework of creating materials with enhanced properties for specific applications including electrodes, capsules, polymer particles and composite films.

The covalent attachment of methoxy-poly(ethylene glycol) (mPEG) is a well established strategy used to improve the pharmaceutical properties of several biomolecules. Since the pioneering work of Abuchovsky, PEGylation has emerged as a powerful technology of significant relevance, not only for the development of new and better drugs, but also for application in material science. Peptides and proteins are the most traditional targets for PEGylation due to their intense and diverse biotechnological applications. The terminal amino group, as well as the ε-amino group of lysine and the thiol group of cysteine, are all well known nucleophilic sites that have traditionally been used to couple peptides and proteins to mPEG derivatives. Advances in the methods for preparation of the mPEG starting materials, together with a careful selection of new mPEG functional end-groups have allowed new reactive mPEGs to emerge, which show narrow polydispersity and controlled reactivity, providing more homogeneous conjugates. In the last few years the trend has moved towards site-selective, reversible and enzymatic PEGylation using a new generation of tailor-made reagents and strategies. The main goal of this article is to present some of the most relevant achievements obtained in the PEGylation of peptides and proteins. The chemistry underlying the current methods used for the preparation of mPEG reagents, as well as the chemistry involved in the PEGylation reactions are presented in detail, in order of stimulating the synthetic and polymer chemist to turn their attention in this fascinating multi and interdisciplinary field of research.

Transition-metal-catalyzed aryl-aryl coupling though C-H bonds activation, termed direct arylation, has been widely used in synthesis of a broad range of small molecules. In contrast to traditional coupling methods such as Suzuki coupling and Stille coupling, direct arylation does not involve tedious preparation of unstable, toxic organometallic reagents. Despite these advantages, direct arylation has not been applied to synthesis of π-conjugated polymers until recently. In this perspective, we summarize the progress of direct arylation polymerization for synthesis of various π-conjugated polymers, including homopolymers of polythiophene derivatives and donoracceptor alternating copolymers. We also discuss present challenges and future directions of this nascent methodology of polymerization for synthesis of functional π-conjugated polymers that can find applications in optoelectronic devices such as solar cells and field effect transistors.