Chain Units Research Articles

Dynamic covalent polymer brushes: reversible surface modification of reactive polymer brushes with alkoxyamine-based dynamic covalent bonds

Reactive poly(methacrylate)-based polymer brushes with radically exchangeable alkoxyamine units in the side chains were prepared on flat silicon substrates and their reactivity and surface properties were investigated. The reactive polymer brushes were prepared by surface-initiated atom transfer radical polymerization (ATRP) and the graft density of the brushes was estimated to be approximately 0.36 chains per nm2. Radical crossover reactions among the alkoxyamine units in the side chains of the polymer brushes and at the ends of the fluorinated polymer chains were carried out to produce polymer brushes with low surface free energies. Angular-dependent X-ray photoelectron spectroscopy (XPS) measurement suggested that the fluorinated polymer chains were predominantly attached to the outermost surface because of the size exclusion from the high graft density. In addition, the de-grafting reaction of the fluorinated polymer chains was also performed to confirm the reversibility of the radical crossover reactions. The surface properties of the polymer brushes after the grafting and de-grafting processes were characterized by XPS and contact angle measurements. The composition calculated from the XPS indicated that the reversible grafting of the fluorinated polymer chains proceeded successfully. The surface wettability of the polymer brushes also changed after the grafting of the fluorinated polymers. Furthermore, after the de-grafting of the fluorinated polymer chains, the peaks attributed to fluorine atoms completely disappeared from the XPS spectrum and the wettability of the surface after the de-grafting returned to that obtained before grafting.

α-N-Acetylgalactosaminidase from Infant-associated Bifidobacteria Belonging to Novel Glycoside Hydrolase Family 129 Is Implicated in Alternative Mucin Degradation Pathway

Bifidobacteria inhabit the lower intestine of mammals including humans where the mucin gel layer forms a space for commensal bacteria. We previously identified that infant-associated bifidobacteria possess an extracellular membrane-bound endo-α-N-acetylgalactosaminidase (EngBF) that may be involved in degradation and assimilation of mucin-type oligosaccharides. However, EngBF is highly specific for core-1-type O-glycan (Galβ1-3GalNAcα1-Ser/Thr), also called T antigen, which is mainly attached onto gastroduodenal mucins. By contrast, core-3-type O-glycans (GlcNAcβ1-3GalNAcα1-Ser/Thr) are predominantly found on the mucins in the intestines. Here, we identified a novel α-N-acetylgalactosaminidase (NagBb) from Bifidobacterium bifidum JCM 1254 that hydrolyzes the Tn antigen (GalNAcα1-Ser/Thr). Sialyl and galactosyl core-3 (Galβ1-3/4GlcNAcβ1-3(Neu5Acα2-6)GalNAcα1-Ser/Thr), a major tetrasaccharide structure on MUC2 mucin primarily secreted from goblet cells in human sigmoid colon, can be serially hydrolyzed into Tn antigen by previously identified bifidobacterial extracellular glycosidases such as α-sialidase (SiaBb2), lacto-N-biosidase (LnbB), β-galactosidase (BbgIII), and β-N-acetylhexosaminidases (BbhI and BbhII). Because NagBb is an intracellular enzyme without an N-terminal secretion signal sequence, it is likely involved in intracellular degradation and assimilation of Tn antigen-containing polypeptides, which might be incorporated through unknown transporters. Thus, bifidobacteria possess two distinct pathways for assimilation of O-glycans on gastroduodenal and intestinal mucins. NagBb homologs are conserved in infant-associated bifidobacteria, suggesting a significant role for their adaptation within the infant gut, and they were found to form a new glycoside hydrolase family 129.

Polymerization and Corrosion Inhibition Effects of Carboxylic Acid Copolymer Containing PEG Side Chain

We designed water soluble copolymer for corrosion inhibition effects in aqueous enviroment. This copolymer was pursued for the goal of environmental adaptability. Water soluble copolymers were prepared from methoxypolyethylene glycol methacrylate (MPEG-MA) and acrylic acid units. We polymerized 5 to 65wt% of methoxypolyethylene glycol methacrylate and 95 to 35wt% of acrylic acid monomers by azobisisobutyronitrile (AIBN) and sodium peroxodisulfate in organic and water media, respectively. The solution containing these copolymers was evaluated inhibition of corrosion effect for steel materials. These results suggested that combination of MPEG-MA and acrylic acid in polymerizing in water media was most effective to inhibit corrosion for steel materials. It is important to contain 4 to 6 mol unit of ethylene oxide side chain in MPEG-MA.

Improved localized surface plasmon resonance biosensing sensitivity based on chemically-synthesized gold nanoprisms as plasmonic transducers

Supporting substrate attached gold nanostructures display localized surface plasmon resonance (LSPR) properties at the visible and near-infrared (NIR) wavelengths. The LSPR wavelength is very responsive to the refractive index of the surrounding medium, allowing simple label-free biosensing when biomolecules are irreversibly adsorbed onto nanostructures. Herein, we show that chemically synthesized gold nanoprisms with 22 nm average edge lengths are very efficient plasmonic transducers for label-free biosensing. The LSPR properties of gold nanoprisms on silanized glass substrate were investigated and readily influenced by bulk refractive index changes and local changes very close to the sensing surface due to the analyte adsorption. The nanoprisms had a 583 nm/RIU (1.62 eV/RIU) refractive index sensitivity and a 4.9 figure of merit (FOM). In addition, the nanoprism surface was modified with straight chain alkanethiols. The LSPR wavelength (λmax) of chemisorbed nanoprisms on glass was very sensitive to surface modification by straight chain alkanethiols and linearly red-shifted by 2.5 nm with every methylene unit of the alkanethiol chain. Importantly, the biotin functionalized nanoprisms displayed red-shifts in λmax upon streptavidin (SA) binding. The lowest SA concentration was measured to be 50 pM, much lower than gold nanospheres, nanorods, bipyramids, and nanostars.

Ordering and Large-Scale Relaxation Properties of Macromolecules in Ferroelectric Polymer Films

Dynamical equations for transverse and longitudinal mean projections of elastic-deformed kinetic chain units (Gaussian subchains) with anisotropic local intra- and interchain orientation interactions of dipolar type and spectra of relaxation times for large-scale motions of the chains in an isotropic and ordered state were obtained. The long-range orientation planar order in the 3D-layered systems leads to an anisotropy of large-scale relaxation properties of the chains (relative to the axis perpendicular to layers). The anisotropy increases with increase of the chain bending rigidity, the strength of interchain interactions and decrease of the scale of its motion. It disappears for most large-scale motions of chains.

Tacticity of poly(butyl-α-cyanoacrylate) chains in nanoparticles: NMR spectroscopy and DFT calculations

NMR spectroscopy and quantum chemical calculations were applied for structural characterization and determination of the preferred stereochemical sequence distribution of the monomer units in the homopolymer chains of poly(butyl-α-cyanoacrylate) nanoparticles. The stereochemical sequence distribution of the monomer units was defined by analysis of their high-resolution 1D 1H and 13C NMR and 2D J-resolved, 1H/13C HSQC and 1H/13C HMBC NMR spectra. The results were verified by employment of B3LYP/6-31G(d) calculations and are consistent with the preferred tendency of polymer chains of PBCN to adopt syndiotactic placements. The proton and carbon chemical shielding were calculated at BPW91/6-31+G(2d,p) level using the GIAO approach and B3LYP/6-31G(d) optimized geometry.

Natrolite is not a "soda-stone" anymore: Structural study of alkali (Li+), alkaline-earth (Ca2+, Sr2+, Ba2+) and heavy metal (Cd2+, Pb2+, Ag+) cation-exchanged natrolites

We report here the preparation and structural models of alkaline-earth (Ca2+, Sr2+, Ba2+) and heavy metal (Cd2+, Pb2+, Ag+) cation-exchanged natrolites at ambient conditions and compare them to the alkali (Li+, Na+, K+, Rb+, Cs+) cation forms. The latter two groups all crystallize in the orthorhombic Fdd 2 symmetry as the natural sodium natrolite, whereas the alkaline earth analogues are all found in the monoclinic Cc symmetry as scolecite, the natural calcium counterpart. We find the existence of a universal linear relationship between the unit-cell volume and the non-framework cation radius in natrolite. The rotation angles of the fibrous chain units are distributed between 25.5° (Li-form) and 2.9° (Cs-form) to show its inverse proportionality to the non-framework cation radius and the channel opening area. We also propose a possible threshold in the cation radius that dictates the distribution pattern of the non-framework cations and water molecules in the ordered and disordered fashions in natrolite.

Synthesis and properties of novel aromatic polyamides with non-conjugated bichromophoric units in the main chains

A dicarboxylic acid bearing two cinnamic acids units linked in their para positions by a methylene bridge was synthesized by the reaction of 4,4′-methylene-bis(benzaldehyde) and malonic acid, characterized by spectral and elemental analysis and used to prepare a series of novel photocrosslinkable aromatic polyamides through its reaction with various ether-bridged aromatic diamines. 1H and 13C NMR, IR and UV spectroscopy confirmed the structure of the monomer and photopolymers. The resulting polymers with inherent viscosities of 0.65–1.14 dL/g were soluble in polar aprotic solvents, such as DMF, DMSO, DMAc and NMP, and showed good film-forming properties. Their weight-average and number-average molecular weights, determined by GPC (polystyrene standard), were in the range 57,400–84,300 and 24,000–40,900, respectively. The percent of water absorbed at 65% relative humidity varied between 1.57% and 2.35%. The polyamides exhibited glass transition temperatures between 202 and 239 °C, and they were stable up to a temperature of 350 °C in air. Wide-angle X-ray scattering diagrams did not show any crystalline reflection and no endothermic peak attributable to polymer melting was observed in DSC curves of the polymers. These photosensitive polymers exhibited strong UV absorption maxima both in solution and film state, and displayed three photochemical transformations under the UV exposure, viz. a trans-cis isomerization, favored in the early stage of UV irradiation, a bimolecular cyclodimerization, leading to the generation of a cyclobutane ring, and a photo-Fries rearrangement evidenced only in polymer solutions.

Novel vitamin E forms in leaves of Kalanchoe daigremontiana and Phaseolus coccineus

In the present study, we isolated novel tocochromanols from green leaves of Kalanchoe daigremontiana and primary leaves of etiolated seedlings of Phaseolus coccineus that were identified as β-, γ-, and δ-tocomonoenols with unsaturation at the terminal isoprene unit of the side chain. The content of γ-tocomonoenol in leaves of etiolated bean increased gradually with the age of seedlings, reaching 50% of the γ-tocopherol level in 40-day-old plants. The content of this compound in leaves was increased by short illumination of etiolated plants and by addition of homogentisic acid, a biosynthetic precursor of tocopherols. These data indicated that γ-tocomonoenol is synthesized de novo from homogentisic acid and tetrahydro-geranylgeraniol diphosphate, a phytol precursor. Based on these results, a biosynthetic pathway of tocomonoenols is proposed.

Crystal modulus of a new semiaromatic polyamide 9-T

The elastic modulus (El) of crystalline regions in the direction parallel to the chain axis in a new semiaromatic polyamide 9-T (PA9-T) containing a long aliphatic chain unit was measured by X-ray diffraction and the derived El value was discussed in terms of its molecular conformation and mechanical properties. For low and high molecular weight PA9-Ts, the El value of 40 GPa was obtained. The low El value for PA9-T is due to the presence of aromatic groups with long crankshaft arms, which result in a greater moment of force during deformation compared with those polymers with planner zigzag molecular conformation like polyethylene and nylon 6 α-form. Another factor for the low El is due to the contraction of its molecular chains that is likely originated from the existence of a torsional conformation. The presence of contraction causes some internal rotation in the polymer chain during extensional deformation, which results in low El. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

New cohort of optically active nanostructure poly(amideimide)s: Production and properties

Novel aromatic-aliphatic poly(amide-imide)s containing chiral units in the main chain and hydroxyl benzamide units in the side chain have been obtained from the step-growth polymerization of 3,5-diamino-N-(4-hydroxyphenyl) benzamide (2) with different chiral diacid chlorides (1a–1e). Theoretical calculations were done by means of computational chemistry methods to narrate the stable conformation and orientation of each diacid chloride monomers under reaction conditions. These polymers were characterized by conventional techniques. The resulting polymers show good thermal stability. Other physical properties of polymers including crystallinity, inherent viscosity and morphological characteristics were also studied.

Access to Antigens Related to Anthrose Using Pivotal Cyclic Sulfite/Sulfate Intermediates

Anthrose is the upstream terminal unit of the tetrasaccharide side chain from a major glycoprotein of Bacillus anthracis exosporium and is part of important antigenic determinants. A novel entry to anthrose-containing antigens and precursors is described. The synthetic route, starting from D(+)-fucose, makes use of intermediates featuring a cyclic sulfite or sulfate function which serves successively as a protecting and a leaving group.

Pure blue electroluminescent poly(aryl ether)s with dopant-host systems

A series of novel arylene ether polymers (P5F-BCzVFs) containing both pentafluorene (5F) and distyrylarylene derivative (BCzVF) units in the side chains for efficient pure blue light emission were prepared by a facile, metal-free condensation polymerization. The emission spectra indicated that color tuning could be achieved through efficient Förster energy transfer from the deep-blue 5F host to the pure-blue BCzVF dopant. Single-layer polymer light-emitting diodes (PLEDs) based on P5F-BCzVFs (ITO/(PEDOT:PSS)/polymer/Ca/Al) exhibited voltage-independent and stable pure blue emission with a Commission International de L'Eclairage (CIE) coordinate of (0.15, 0.15), a maximum brightness of 3576 cd/m2, and a maximum luminous efficiencies of 2.15 cd/A, respectively. As most polymers with dopant-host systems, the luminous efficiencies of all P5F-BCzVFs surpassed that of the host-only polymer (P5F), due to the energy transfer and charge trapping from the host to the dopant. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A Novel, Bipolar Polymeric Host for Highly Efficient Blue Electrophosphorescence: a Non‐Conjugated Poly(aryl ether) Containing Triphenylphosphine Oxide Units in the Electron‐Transporting Main Chain and Carbazole Units in Hole‐Transporting Side Chains

A novel, bipolar polymeric host based on a poly(aryl ether) containing phosphine oxide units in the electron-transporting main chain and carbazole units in the hole-transporting side chains is designed and synthesized for blue electrophosphorescence. This polymeric host possesses a bipolar character and a high E(T) of 2.96 eV. The efficiency of blue-emitting PhPLEDs based on this polymeric host doped with Flrpic reaches 23.3 cd A(-1) (EQE = 10.8%).

Effect of block compositions of amphiphilic block copolymers on the physicochemical properties of polymeric micelles

Amphiphilic block copolymers with various chain lengths of poly( n-butyl methacrylate) blocks (PBMA) and poly( N-acryloylmorpholine) blocks (PAM) were prepared by RAFT polymerization. Packing parameter of block polymers in water ( β < 0.2) indicated the formation of core-corona structures, which was further confirmed from a difference between core- and corona-forming chain surface areas. Hydrodynamic micellar size was related with the numbers of BMA ( N BMA) and AM ( N AM), and their ratios ( N BMA/ N AM). With increasing N BMA/ N AM value, the polymer aggregation numbers and inner core sizes increased, while the critical micelle concentrations, the corona thickness, and the second virial coefficient of block copolymer micelles decreased. These properties changed with increasing N BMA/ N AM value resulted in a linear increase in corona chain unit density ( ρ AM) that limited chain mobility. Thus, the interaction between the micelles and serum protein at low ρ AM disappeared at a higher value. Consequently, both micellar properties and biocompatible effect can be regulated by tailoring the block compositions of amphiphilic polymers.

Dissipative particle dynamics simulation on the association properties of fluorocarbon-modified polyacrylamide copolymers

The hydrophobic association properties of a modified polyacrylamide (HMPAM) solution are attributed to the composition of the solution and environmental factors. In this study, the hydrophobic association of fluorocarbon-modified polyacrylamide aqueous solutions has been investigated on a mesoscopic level by considering the variation of root mean square (RMS) end-to-end distances using dissipative particle dynamics (DPD) simulations. The hydrophobic association depends on the hydrophobic behavior of the groups incorporated, the environmental temperature, the addition of salts and the shear. The embedded fluorocarbon units in the polyacrylamide chains are trifluoroethyl methacrylate, hexafluorobuyl methacrylate and dodecafluoroheptyl methacrylate, respectively, and the corresponding copolymers are expressed as P(AM-AANa-3F), P(AM-AANa-6F) and P(AM-AANa-12F). The modeling results show that P(AM-AANa-12F) has the strongest hydrophobic interactions among the three copolymers. The hydrophobic association of P(AM-AANa-12F) solutions in pure water is lower than that of corresponding salt-water solutions and shows stronger positive salinity sensitivity. P(AM-AANa-12F) can maintain its hydrophobic association in aqueous solution at high temperature, and its three-dimensional network can be reformed after shear. These conclusions are consistent with the experimental and theoretical results. The hydrophobic association of fluorocarbon-modified polyacrylamide aqueous solutions has been investigated on a mesoscopic level by considering the variation of root mean square (RMS) end-to-end distances using dissipative particle dynamics (DPD) simulation. Its hydrophobic association property is affected by the type of the hydrophobic group, salt, temperature and shear. The unit of stronger hydrophobic property within the chain makes the macromolecule have the greatest association in the solution.

How Linear Is “Linear” Polyaniline?

The structure of emeraldine salt and emeraldine bases with different molar weight and their behavior in electrochemical doping was studied by different spectroscopic and spectroelectrochemical techniques. By Fourier transform infrared (FTIR) spectroscopy, the branching of the polymer chain at tri- and tetrasubstituted benzene rings as well as the presence of small amounts of phenazine units are shown. The branching of the polymer chains increases with the increasing of the molar weight of emeraldines. The optical transitions in protonated and unprotonated emeraldine were studied by ultraviolet-visible near-infrared (UV-vis NIR) spectroscopy. By comparison of the electron spin resonance (ESR) spectra of emeraldine in protic solvents and acidic solutions, the emeraldine bases are shown to be to some extent protonated. Applying in situ ESR-UV-vis NIR spectroelectrochemistry, the charged states in emeraldines upon p-doping were investigated considering the influence of the nonideal "linear" polymer structures. The initial stage of oxidation of the emeraldine base and salt consists of the different charged states. The phenazine units in the polymer chains stabilize the charged states in the emeraldines upon p-doping.

ESI Single Quadrupole Mass Spectrometric Investigation of Polyhydroxy Acids

ESI-MS spectra were recorded with a FIA-MS system under CID conditions for 19 polyhydroxy carboxylic acids to assess the analytical selectivity of single quadrupole MS and to evaluate its suitability for the qualitative identification of the target compounds. Suited ESI operation conditions were defined for several sugar acids and their lactones and the pH dependence of the respective acid-lactone conversion was investigated. Besides the common neutral mass losses of H2O and CO2 specific mass losses, presumably belonging to the release of small carbon chain units, were established for isocitric and gluconic acids. A product ion with m/z 75 was part of the MS spectra of all aldonic acids, potentially indicating this structural subgroup of sugar acids. The spectra of other sugar acids and of tartaric, isocitric and shikimic acids had a product ion with m/z 73 in common. The results reveal that the CID mass spectra of several hydroxy acids show characteristic product ion patterns suited for a selective analyte identification.

Polymerization mechanism of trimethylene carbonate carried out with zinc(II) acetylacetonate monohydrate

The proposed mechanism of initiation and course of ring-opening polymerization of cyclic trimethylene carbonate (TMC) involving zinc(II) acetylacetonate is in accordance with the mechanism of monomer activation. At the first stage of the process, coordination of carbonate to Zn(Acac)2·H2O complex occurs with the release of weakly coordinated water molecules. This free water molecule reacts with active TMC–Zn(Acac)2 complex. The reaction results in the formation of propanediol and CO2 emission. During further stages of the investigated process, the formed propanediols, or later the oligomeric diols produced with polymerization, are cocatalysts of the chain propagation reaction. The chain propagation occurs because of repeating activation of the TMC monomer through the creation of an active structure resulting in the exchange/transfer reaction between the zinc complex and the monomer, with its following attachment to the hydroxyl groups, carbonate ring opening, and formation of the carbonic unit of polymer chain. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Adsorption of amphiphilic comb-shaped macromolecules on a patterned surface

The molecular-dynamics method is used to study the adsorption of A-graft-B macromolecules on patterned planar surfaces consisting of regions a and b that specifically interact with chain units. Surfaces with patterns in the form of circles of different radii and a spiral stripe are discussed. Effective recognition occurs during the adsorption of an A-graft-B macromolecule on these patterned surfaces. Recognition means that, for a proper combination of the architecture of a macromolecule and the energy parameters of its interaction with the plane regions, the macromolecule can be located along the boundary of a circle with a given radius or can stay in a given location of the spiral stripe.