Graphene was produced from graphite powder using the three best known water-based conversion approaches. The first two are based on chemical oxidation methods, only differing in the reduction process, either by the use of hydrazine or by thermal expansion, respectively. The third one is based on long-term ultrasonic exfoliation. Water/surfactant solutions were prepared with these three nanofillers and latex technology concept was applied for the preparation of conductive graphene/polystyrene composites with well-dispersed graphene platelets. The samples were characterized with respect to filler properties and morphology, and their influences on electrical conductive properties of the composites were compared. Microscopic studies showed that both reduction processes lead to agglomeration/wrinkling of the platelets, even though they yield composites with high conductivity and low percolation threshold. Although mechanical ultrasound exfoliation of graphite produces less defective multi-layer graphene, these platelets have a smaller lateral size and their composites exhibit a higher percolation threshold. Differences in electronic transport behavior were observed, which suggest direct contact transport competing with tunneling. (C) 2015 Elsevier Ltd. All rights reserved.

Block copolymers consisting of a polyethylene block and a polar polymer block are interesting structures for the compatibilization of polyethylene/polar polymer blends or polyethylene-based composites. Since the synthesis of polyethylene-based block copolymers is an elaborate process, diblock copolymers consisting of "polyethylene-like" poly-(pentadecalactone) (PPDL) and poly(L-lactide) (PLLA) were synthesized using a one-pot, sequential-feed ring-opening polymerization of pentadecalactone (PDL) and L-lactide (LLA). The peculiar activity of the used aluminum salen catalysts yielded a block copolymer consisting of two blocks with both a high dispersity, as a result of intra block transesterification. Interestingly, interblock transesterification was effectively suppressed. The obtained poly(PDL-block-LLA) of various block lengths showed coincidental crystallization of the two blocks with an associated microphase-separated morphology, in which PLLA. spheres with a high dispersity are distributed within the PPDL matrix. The complex morphologies is believed to arise from the presence of a whole range of block sizes as a consequence of the large dispersity of both blocks. The application of these block copolymers as compatibilizers for high density polyethylene (HDPE)/PLLA blends led to a clear change in blend morphology and a steep decrease in particle size of the dispersed phase. Furthermore, addition of the block copolymers to blends of linear low density polyethylene (LLDPE) and PLLA led to a significant increase in adhesion between the two phases. For both HDPE/PLLA and LLDPE/PLLA blends, the compatibilization efficiency of the poly(PDL-block-LLA) increased when the length of the PPDL block was increased. The presented results clearly show that PPDL can function as a substituent for various types of polyethylene, which opens up a new method for compatibilizing polyethylene with polar polymers using easy attainable "PE-like" block copolymers.

A wide range of polymers were prepared from biomass-derivatives, using different polymerization mechanisms. Well-defined, fully hydroxy-functional polyesters based on aliphatic diols were synthesized, using either conventional metal-based catalysts or the organic superbase 1,5,7-triazabicyclododecene (TBD). Unsaturated polyesters were also made, offering additional functionality to these biobased resins. Metal-catalyzed or enzymatic ring-opening polymerization of macrolactones afford novel, renewable materials with good mechanical properties similar to those of polyethylene. In addition to polyesters, aliphatic polycarbonates based on 1,4:3,6-dianhydrohexitols (DAH) were prepared, which proved very suitable for application in thermosetting coating systems. Polyamides from sebacic acid, 1,4-diaminobutane and diaminoisoidide are very interesting polymers, in which the diaminoisoidide residues cocrystallize in the polyamide 4.10 matrix. Another type of polymers studied were the polyurethanes. Thermoplastic polyurethanes and polyureas from biomass can be effectively synthesized through either isocyanate-based or isocyanate-free strategies. Also, poly(ester/carbonate urethane) networks from renewable polymer resins are very promising systems for coating

Combining controlled radical polymerizations and a controlled polypeptide synthetic technique, such as N-carboxyanhydride (NCA) ring-opening polymerization, enables the generation of well-defined block copolymers to be easily accessible. Here we combine NCA polymerization with the nitroxide-mediated radical polymerization of poly(n-butyl acrylate) (PBA) and polystyrene (PS), using a TIPNO and SG1-based bifunctional initiator to create a hybrid block copolymer. The polypeptide block consists of (block) copolymers of poly(l-glutamic acid) embedded with various quantities of l-alanine. The formed superstructures (vesicles and micelles) of the block copolymers possessed varying degrees of enzyme responsiveness when exposed to elastase and thermolysin, resulting in controlled enzymatic degradation dictated by the polypeptide composition. The PBA containing block copolymers possessing 50% l-alanine in the polypeptide block showed a high degradation response compared to polymers containing lower l-alanine quantities. The particles stabilized by copolypeptides with l-alanine near the hydrophobic block showed full degradation within 4 days. Particles containing polystyrene blocks revealed no appreciable degradation under the same conditions, highlighting the specificity of the system and the importance of synthetic polymer selection. However, when the degradation temperature was increased to 70 °C, degradation could be achieved due to the higher block copolymer exchange between the particle and the solution. A number of novel biohybrid structures are disclosed that show promise as enzyme-responsive materials with potential use as payload release vehicles, following their controlled degradation by specific, target, enzymes.

The phosphorus-containing aliphatic-aromatic diol 2-[4-(2-hydroxy-ethoxy)-3-(10-oxo-10-H9-oxa-10-lambda 5-phospha-phenanthrene-10-yl)-phenoxy]-ethanol, a potential flame retardant, was incorporated into poly(butylene terephthalate) (PBT) by solid state polycondensation. Thus, polymers with various ratios of PBT/DOPO-diol and number-average molar masses up to 57,000 g mol(-1) could be prepared. Their molar masses were higher than those of copolyesters with comparable composition obtained by direct melt polycondensation. Structures and properties of copolyesters produced by both methods were not significantly different after melt processing. Their thermal properties and combustion behaviour were investigated by means of DSC, TGA, and pyrolysis combustion flow calorimetry. Combustion studies revealed high char yields, very low heat release capacities and high limiting oxygen index (LOI) at rather low P-contents, indicative of better flame-retardancy properties. (C) 2010 Elsevier Ltd. All rights reserved.

The potential of polystyrene/polymethylphenylsiloxane (PS/PMPS) blends as a matrix for nanocomposites is investigated. It was proven by dynamic rheometry and conductivity measurements that PMPS effectively disperses carbon nanotubes, as was already known for polydimethylsiloxane (PDMS). The phase behaviour of PS/PMPS blends was investigated using differential scanning calorimetry or modulated temperature differential scanning calorimetry. The blends were found to exhibit partial miscibility, in contrast to the known immiscible behaviour of PS/PDMS blends. A miscibility window exists for PS/PMPS blends containing less than approximately 10 wt% PMPS.

We have investigated a novel approach to well-defined peptide-decorated cross-linked nanoparticles. The particles were obtained from well-defined poly(gamma-benzyl-L-glutamate-b-styrene) block copolymers with active nitroxide end-groups by reaction with divinylbenzene (DVB). The block length ratio and the amount of cross-linker (DVB) were systematically varied. Molecular weights of the cross-linked particles up to 548 000 g/mol with polydispersities around 1.5 were confirmed by size-exclusion chromatography. A clear dependence of the molecular weight from the block length ratio and the amount of crosslinker was observed. This was confirmed by dynamic light scattering results revealing the formation of nanoparticles up to 21 nm in size. The core-shell structure was evident from the TEM micrographs. Further deprotection of the peptide shell yielded water-soluble pH-responsive nanoparticles with a poly(L-glutamic acid) shell and a polystyrene core. Cryo-TEM micrographs confirmed the presence of individual core-shell particles in the aqueous solution.

Polypendadecalactone has properties comparable to polyethylene. Enzymatic polymerisation affords polymers with high molecular weight, which can be spun into fibres with high crystalline order and strength.

The polymerization of N-carboxyanhydride (NCA) at low temperatures is controlled and allows the synthesis of a variety of well-defined polypetides.

The surface functionalization of macroporous polyHIPE (pHIPE) was achieved by Huisgen-type 'click' chemistry. In the first step a 600-800 nm thick layer of poly(glycidyl methacrylate) (pGMA) was grafted from the pHIPE surface by atom transfer radical polymerization (ATRP). Near quantitative azidation of the pGMA layer was achieved by the ring-opening reaction of the epoxide groups with sodium azide. The influence of the reaction conditions on the uniformity of the 'click' reaction on the three-dimensional macroporous materials was shown in model reactions with propargyl alcohol. Under optimized conditions, azide conversions of around 80% were estimated from IR-spectra. Visualization of the homogeneous functionalization was achieved by the attachment of a fluorescent molecule. Moreover, the first proof of the versatility for biofunctionalization of pHIPE by this method was provided by the attachment of several protected amino acids. The hydrolytic stability of the triazole ring allows for the successful deprotection of the amino acids on the pHIPE.

The synthesis of polypeptide-containing block copolymers combining N-carboxyanhydride (NCA) ring-opening polymerization and atom transfer radical polymerization (ATRP) was investigated. An amide initiator comprising all amine function for the NCA polymerization and an activated bromide For ATRP was used. Well-defined polypeptide macroinitiators were obtained from gamma-benzyl-L-glutamate NCA, O-benzyl-serine NCA, and N-benzyloxy-L-lysine. Subsequent ATRP macroinitiation from the polypeptides resulted in higher than expected molecular weights. Analysis of the reaction products and model reactions confirmed that this is due to the high frequency of termination reactions by disproportionation in the initial phase of the ATRP, which is inherent in the amide initiator structure In some cases selective precipitation could be applied to remove unreacted macroinitiator to yield well-defined block copolymers. (C) 2009 Wiley Periodicals, Inc J Polym Sci Part A Polym Chem 47. 6883-6891, 2009

The production of poly(butylene terephthalate) (PBT) struggles with the formation of substantial amounts of tetrahydrofuran (THF). When PBT is synthesized from terephthalic acid (TPA) instead of dimethyl terephthalate (DMT), even more THF is formed, mainly during the first stage of the melt polymerization process. Although a lot of literature reports on the existence of this side reaction in both processes, to the best of our knowledge, a comparison, which reveals the importance of the acidity and insolubility of TPA on the THF formation, was never described. Finally, an interesting study was performed on the THF formation during the synthesis of PBT from mixtures of DMT and TPA as well as from the completely soluble monomethyl terephthalate (MMT). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2427-2434, 2009

Well-defined cysteine-containing synthetic polypeptides were synthesised and the versatility of various chemical reactions on these thiol groups was investigated.

An in depth study is performed on the origin of and influences on the formation of tetrahydrofuran (THF) during the first stage of the terephthalic acid (TPA) based synthesis of poly(butylene terephthalate) (PBT). Although many improvements on the synthesis process of PBT have been reported in literature to suppress this undesired side reaction, only few studies reported on the actual mechanism of the THF formation, which is not completely understood. Low molecular weight compounds have been used to model the side reactions occurring during the polymerization reaction. It could be concluded that, in contrast to previous reportage, only the THF formation from the monomer, 1,4-butanediol, is directly influenced by the use of TPA as a starting material for the production of PBT. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2435-2444, 2009

We present a detailed study of the influence of carbon nanotube (CNT) characteristics on the electrical conductivity of polystyrene nanocomposites produced using a latex‐based approach. We processed both industrially‐produced multi‐wall CNT (MWCNT) powders and MWCNTs from vertically‐aligned films made in‐house, and demonstrate that while the raw CNTs are individualized and dispersed comparably within the polymer matrix, the electrical conductivity of the final nanocomposites differs significantly due to the intrinsic characteristics of the CNTs. Owing to their longer length after dispersion, the percolation threshold observed using MWCNTs from vertically‐aligned films is five times lower than the value for industrially‐produced MWCNT powders. Further, owing to the high structural quality of the CNTs from vertically‐aligned films, the resulting composite films exhibit electrical conductivity of 103 S m−1 at 2 wt% CNTs. On the contrary, composites made using the industrially‐produced CNTs exhibit conductivity of only tens of S m−1. To our knowledge, the measured electrical conductivity for CNT/PS composites using CNTs from vertically‐aligned films is by far the highest value yet reported for CNT/PS nanocomposites at this loading.

The ability of a MgCl2 support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily effective for zirconocene activation. A highly disordered support prepared by the reaction of MgBu2 with HCl gave high activity with TiCl4 but low activity with (n-PrCP)(2)ZrCl2. High polymerization activities with the zirconocene were only obtained with supports of type MgCl2/AIR(n)(OEt)(3-n) prepared from the reaction of AlR3 with MgCl2 center dot 1.1EtOH. These supports are characterized by additional peaks in the X-ray diffraction pattern, indicating the presence of a crystalline structure which is absent in the other supports and contains highly Lewis acidic sites able to generate the active metallocenium species.

During nonisothermal crystallization of highly dispersed polypropylene/carbon nanotube (CNT) composites, considerable heterogeneous nucleation is observed to an extent scaling with the CNT surface area. Saturation occurs at higher loadings, reaching a plateau value for the crystallization onset which is 15 °C higher than in the unfilled matrix. Polymorphic behavior does not occur, as revealed from wide-angle X-ray diffraction. Upon subsequent heating, an increase in the melting temperature is observed due to increased crystalline perfection in the presence of CNTs. The complex multiple melting behavior is interpreted in terms of recrystallization phenomena. A study at varying heating and cooling rates reveals that CNTs affect the chain segment mobility of the matrix and largely inhibit recrystallization upon heating. TEM observation of the nanocomposite morphology evidences the occurrence of a transcrystalline layer around the CNTs. A structure model is presented, in which individually dispersed CNTs are separated from a bulklike polymer phase by a highly ordered crystalline interface with reduced polymer mobility.

We systematically investigated a series of polymers derived from macrolactones, namely, pentadecalactone, hexadecalactone, and their unsaturated analogues ambrettolide and globalide as potential biomaterials. By enzymatic ring-opening polymerization these monomers can conveniently be polymerized to high molecular weight. The polymers are highly crystalline with melting points around 95 degrees C for the saturated polymers and lower melting points for the unsaturated polymers (46-55 degrees C). All polymers are nontoxic as measured by an MTT assay for metabolic cell activity of a 3T3 mouse fibroblast cell line. Degradation studies showed no hydrolytic or enzymatic degradability of the polymers, which was ascribed to the high crystallinity and hydrophobicity of the materials. The unsaturated polymers were cross-linked in the melt, yielding fully amorphous transparent materials with a gel content of 97%.

The effect of cyclopentadienyl ring substitution on the immobilization and activation of zirconocenes on supports of type MgCl2/AlRn(OEt)(3-n) has been investigated. Comparison of the activity of immobilized zirconocenes (RCP)(2)ZrCl2 in ethylene polymerization, using simple aluminum alkyls such as AlEt3 or AliBu(3) as a cocatalyst, revealed a remarkable effect of the substituent R in the cyclopentadienyl ring. Low activity (<300 kg/mol bar h) was obtained with R = H or Et, but longer alkyl substituents, notably n-Pr or n-Bu, gave more than an order of magnitude increase in activity. Zirconocenes with branched substituents (i-Pr, t-Bu) were less easily immobilized and gave relatively low activity, while the activities of zirconocenes of composition Cp-(RCp)ZrCl2 (R = n-Pr, n-Bu, n-pentyl) were intermediate between those of CP2ZrCl2 and (RCP)(2)ZrCl2. Experiments carried out under homogeneous conditions with aluminoxane cocatalysts indicated that the effect of cyclopentadienyl ring substitution can be related to differences in the ease of formation of the active species. An inverse relationship between activity and the catalyst loading on the support was found. At a low loading of 1 mu mol (n-PrCP)(2)ZrCl2/g support, an activity greater than 40 000 kg/mol bar h was obtained in ethylene polymerization at 70 degrees C, with AliBu(3) as the cocatalyst. The results demonstrate that with certain MgCl2-immobilized zirconocenes it is possible to achieve very high polymerization activity without the use of methylaluminoxane or a borate activator, but the strong effect of catalyst loading on activity implies the presence of a relatively low number of active species.