Extraction processes reduce polyphosphate ion migration,dispersion and diffusion as detected with gel electrophoresis and 31P DOSY NMR

Inorganic polyphosphates (polyPs) have been identified in eukaryotic and prokaryotic cells alike. Various extraction methods have been optimized as a necessary step before identification and measurement of these polymers. Three commercially available sodium polyP glasses were either dissolved or dissolved and extracted by two commonly used polyP extraction techniques – perchloric acid or buffered phenol–chloroform. The products were separated by polyacrylamide gel electrophoresis (PAGE), stained with toluidine blue O, and the migration results quantitatively compared. Both extraction processes reduced the relative migration distances of the peak and leading edges, and the stained band lengths, suggesting reduced polyP migration and dispersion. ³¹P diffusion-ordered spectroscopy nuclear magnetic resonance confirmed that polyP extraction by perchloric acid or phenol–chloroform processes reduced polyP diffusion coefficients and suggested hydrolytic degradation with stronger end-chain signals. Reduced polyP diffusivity after extraction makes possible an overestimation of synthetic polyP chain length assignment when compared to unextracted polyP ladders with PAGE. The mechanism(s) for reduced synthetic polyP diffusion after extraction and intracellular chemical environment effects on migration are not known.     

Dynamic light scattering of a concentrated multicomponent spherical particle solution

The“measured”dunamic structure function of highly concentrated and smallspherical colloidal system with a narrow distribution of particle sizes can be expressed in termsof the sum of two independent modes due to collective diffusion and polydispersity fluctuationsrespectively.The“measured”static structure functions S~M(K) is derived,and applied to cal-culate the polydispersity distribution.The relationship between the moments of the gammaparticle size distribution and the moments determined by a dynamic light scattering measure-ment is developed for the case when the particles are small and spherical.     

Enthalpies of dilution of aqueous tetradecyltrimethylammonium bromide from 50 to 175°C

Enthalpies of dilution of aqueous tetradecyltrimethylammonium bromide have been measured from 0.3 to about 0.002 mol-kg^–1 and from 323 to 448 K at 1.03 MPa. Different methods of obtaining the enthalpy of micellization from experimental data are examined. Enthalpies of micellization calculated from these methods disagree by large amounts. From consideration of the temperature dependence of the average aggregation number and multiple equilibria equations for micellization, it is shown that there is an enormous dependence of micellizaton enthalpy on aggregation number of a micelle.     

The influence of the molecular weight distribution of network chains on the mechanical properties of polymer networks

End-linked poly(dimethylsiloxane) (PDMS) networks with different molecular weight distributions (MWD) of the primary chains were prepared and investigated by isothermal stress-strain measurements. We found a lowering of the elastic modulus with increasing broadness of the MWD. The observed range of the moduli seems not to be restricted to the region limited by the classical models of rubber elasticity. This result is based on our own experimental investigations and on a reanalysis of data taken from the literature. In the case of nearly monodisperse distributions (M _n /M _w 1) the effect of configurational restrictions of the network strands probably dominates. In the opposite case (M _n /M _w 1), we discuss that spatial clustering of the crosslinks may reduce the effective number of elastically active network junctions.     

“Polymeromics”: Mass spectrometry based strategies in polymer science toward complete sequencing approaches: A review

Mass spectrometry (MS) is the most versatile and comprehensive method in “OMICS” sciences (i.e. in proteomics, genomics, metabolomics and lipidomics). The applications of MS and tandem MS (MS/MS or MSⁿ) provide sequence information of the full complement of biological samples in order to understand the importance of the sequences on their precise and specific functions. Nowadays, the control of polymer sequences and their accurate characterization is one of the significant challenges of current polymer science. Therefore, a similar approach can be very beneficial for characterizing and understanding the complex structures of synthetic macromolecules. MS-based strategies allow a relatively precise examination of polymeric structures (e.g. their molar mass distributions, monomer units, side chain substituents, end-group functionalities, and copolymer compositions). Moreover, tandem MS offer accurate structural information from intricate macromolecular structures; however, it produces vast amount of data to interpret. In “OMICS” sciences, the software application to interpret the obtained data has developed satisfyingly (e.g. in proteomics), because it is not possible to handle the amount of data acquired via (tandem) MS studies on the biological samples manually. It can be expected that special software tools will improve the interpretation of (tandem) MS output from the investigations of synthetic polymers as well. Eventually, the MS/MS field will also open up for polymer scientists who are not MS-specialists. In this review, we dissect the overall framework of the MS and MS/MS analysis of synthetic polymers into its key components. We discuss the fundamentals of polymer analyses as well as recent advances in the areas of tandem mass spectrometry, software developments, and the overall future perspectives on the way to polymer sequencing, one of the last Holy Grail in polymer science.     

Copper Catalyzed ATRP of Methyl Methacrylate Using Aliphatic α-Bromo Ketone Initiator

The atom transfer radical polymerization (ATRP) of MMA was examined using 3-bromo-3-methyl-butanone-2 (MBB) as an initiator in the presence of CuBr as catalyst and 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine (BPIEP) as a tridentate N-donor ligand. The effect of various other N-donor ligands including a bisoxazoline ligand, namely, 2,6-bis(4,4-dimethyl-2-oxazolin-2-yl) pyridine (dmPYBOX) was studied in ATRP and reverse ATRP of MMA. The ATRP of MMA in toluene at 90 °C using MBB as initiator was relatively slow in the case of bidentate and faster in the case of tridentate N-donor ligands. The apparent rate constant, k_app, with MBB as initiator and BPIEP as ligand in toluene (50%, v/v) at 90 °C was found to be 7.15 × 10⁻⁵ s⁻¹. In addition, reverse ATRP of MMA in diphenylether at 70 °C using BPIEP/CuBr₂ as catalyst system was very effective in reducing the reaction time from several hours to 24 h for polymerization of MMA.     

Effect of Nanoparticles on the Phase Behavior of Polystyrene/Poly(vinyl methyl ether) Blends with Different Polydispersities

Effects of two kinds of silica nanoparticles on the phase behavior of blends of poly (vinyl methyl ether) (PVME) and two kinds of polystyrene (PS), with the same number average molecular weight but different polydispersities, were studied by using optical microscopy. The addition of both the hydrophilic A200-SiO₂ and hydrophobic R974-SiO₂ nanoparticles made the miscibility become worse. The decrease in the phase separation temperatures of PS/PVME with polydisperse PS (pPS) was larger than that of PS/PVME with monodisperse PS (mPS) in the presence of A200-SiO₂; the shifts of the phase separation temperatures of mPS/PVME and pPS/PVME were comparable for the incorporation of R974-SiO₂. The addition of both kinds of silica accelerated the phase separation during the nonisothermal phase separation. The domain size changes of the phase morphology of mPS/PVME (50/50) and pPS/PVME (50/50) were almost the same during the nonisothermal phase separation in the presence of nanoparticles. During the isothermal phase separation, the introduction of silica slowed down the phase separation dynamics by hindering the phase structure transition. The morphology changes of pPS/PVME (50/50) were more evident than those of mPS/PVME (50/50) with the incorporation of SiO₂.     

Influence of a reversible addition–fragmentation chain transfer agent in the dispersion polymerization of styrene

Dispersion polymerization was applied to the controlled/living free‐radical polymerization of styrene with a reversible addition–fragmentation chain transfer (RAFT) polymerization agent in the presence of poly(N‐vinylpyrrolidone) and 2,2′‐azobisisobutyronitrile in an ethanol medium. The effects of the polymerization temperature and the postaddition of RAFT on the polymerization kinetics, molecular weight, polydispersity index (PDI), particle size, and particle size distribution were investigated. The polymerization was strongly dependent on both the temperature and postaddition of RAFT, and typical living behavior was observed when a low PDI was obtained with a linearly increased molecular weight. The rate of polymerization, molecular weight, and PDI, as well as the final particle size, decreased with an increased amount of the RAFT agent in comparison with those of traditional dispersion polymerization. Thus, the results suggest that the RAFT agent plays an important role in the dispersion polymerization of styrene, not only reducing the PDI from 3.34 to 1.28 but also producing monodisperse polystyrene microspheres. This appears to be the first instance in which a living character has been demonstrated in a RAFT‐mediated dispersion polymerization of styrene while the colloidal stability is maintained in comparison with conventional dispersion polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 348–360, 2007     

Increase and Decrease of the Effective Conductivity of Two Phase Composites due to Polydispersity

We present a two-dimensional mathematical model of a composite material with conducting inclusions (fibers) embedded in a matrix. Our main objective is to study how polydispersity (two different sizes of particles) affects the overall conductivity of the composite. If the conductivity of inclusions is higher than the conductivity of the matrix, then previous studies suggest an increase of the effective conductivity due to polydispersity. We show that for high volume fraction when inclusions are not well-separated and percolation effects play a significant role, polydispersity may result in either an increase or decrease of the effective conductivity. Our proof is based on the method of functional equations and it provides sufficient conditions for both the increase and the decrease of the effective conductivity.     

Effect of matrix bidispersity on the morphology of polymer-grafted nanoparticle-filled polymer nanocomposites

We present a simulation study showing the effect of bidispersity in matrix homopolymer length on the wetting/dewetting of homopolymer-grafted nanoparticles and the morphology of polymer nanocomposites where the graft and matrix polymer chemistries are identical. In a bidisperse matrix with equal number of short and long chains and average matrix length greater than the monodisperse graft length, the densely grafted polymer layer is preferentially wet by the short chains and relatively dewet by the long chains. This is driven by a larger gain in entropy of mixing between graft and matrix for short matrix chains than long matrix chains. Despite the preferential wetting of the short and dewetting of long chains, matrix length bidispersity does not significantly change the overall wetting of the grafted layer. Unlike graft length bidispersity that significantly improves particle dispersion, matrix length bidispersity slightly increases particle aggregation in the polymer matrix. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1661–1668