Complex Polymer Structures Research Articles

Coordination polymeric structures in the sodium salt of 4-chloro-3-nitrobenzoic acid and the sodium and potassium salts of 4-nitroanthranilic acid

The structures of the hydrated sodium salts of 4-chloro-3-nitrobenzoic acid {poly[aqua(μ4-4-chloro-3-nitrobenzoato)sodium(I)], [Na(C7H3ClNO4)(H2O)]n, (I)} and 2-amino-4-nitrobenzoic acid {poly[μ-aqua-aqua(μ3-2-amino-4-nitrobenzoato)sodium(I)], [Na(C7H5N2O4)(H2O)2]n, (II)}, and the hydrated potassium salt of 2-amino-4-nitrobenzoic acid {poly[μ-aqua-aqua(μ5-2-amino-4-nitrobenzoato)potassium(I)], [K(C7H5N2O4)(H2O)]n, (III)} have been determined and their complex polymeric structures described. All three structures are stabilized by intra- and intermolecular hydrogen bonding and strong π-π ring interactions. In the structure of (I), the distorted trigonal bipyrimidal NaO5 coordination polyhedron comprises a monodentate water molecule and four bridging carboxylate O-atom donors, generating a two-dimensional polymeric structure lying parallel to (001). Intra-layer hydrogen-bonding associations and strong inter-ring π-π interactions are present. Structure (II) has a distorted octahedral NaO6 stereochemistry, with four bridging O-atom donors, two from a single carboxylate group and two from a single nitro group and three from the two water molecules, one of which is bridging. Na centres are linked through centrosymmetric four-membered duplex water bridges and through 18-membered duplex head-to-tail ligand bridges. Similar centrosymmetric bridges are found in the structure of (III), and in both (II) and (III) strong inter-ring π-π interactions are found. A two-dimensional layered structure lying parallel to (010) is generated in (II), whereas in (III) the structure is three-dimensional. With (III), the irregular KO7 coordination polyhedron comprises a doubly bridging water molecule, a single bidentate bridging carboxylate O-atom donor and three bridging O-atom donors from the two nitro groups. A three-dimensional structure is generated. These coordination polymer structures are among the few examples of metal complexes of any type with either 4-chloro-3-nitrobenzoic acid or 4-nitroanthranilic acid.

High Frequency Scanning Acoustic Microscopy as Diagnostic Tool in Tissue Science

The objective of this paper is to demonstrate the feasibility of High Frequency Scanning Acoustic Microscopy (HF SAM) as a tool to characterize biological tissues. The HF SAM is shown to provide both imaging and quantitative stiffness measuring abilities. The plant cell wall is used as a test analog to study the influence on stiffness when one important structural component is removed from a complex polymer structure. In particular, the hypothesis of this work was that the biopolymer pectin may have a strong effect on the mechanical properties of primary plant cell walls. The technical approach was to use HF SAM to document the effect of pectinase enzyme treatment to remove pectin from onion primary cell wall. The novelty in this work was to demonstrate the capability of HF SAM in terms of a characteristic curve called the V(Z) signature. The results indicate a significant change in the V(Z) signature with time into the enzyme treatment. Thus the HF SAM method opens the door to a systematically nondestructive study of complex bio-polymer structures.

Fluctuation limitations on the voxel minimal size at laser nanopolymerization

Laser (or two-photon) nanopolymerization is an effective way of producing 3D polymeric submicron structures. The mainstream in developing this technology is improvement of the spatial resolution of nano-objects. Fluctuation-induced inhomogeneities are studied as the main physical reason limiting the spatial resolution of polymeric structures obtained by nanopolymerization. Typically, complex polymeric structures have the form of a raster composed of many elements, voxels, about 100 nm across. Monte Carlo simulation of a spherically symmetric polymeric voxel is carried out. It is shown that, when the voxel size becomes less than critical, the position and size of a voxel vary from realization to realization (become irreproducible). This effect is attributed to the disappearance of the voxel’s core—part of a voxel that has macroscopic properties. Irreproducible formation of the single voxels may lead to distortions of the fine features of complex microstructures and, hence, to a deterioration of the spatial resolution. Estimates are made of the minimal size of voxels that can be reproducibly produced in real laser experiments.

Hot embossing at viscous state to enhance filling process for complex polymer structures

In this paper, a new hot embossing process, molding at the viscous state, for fabrication of complex polymer structures at the micro and millimeter scale is presented. Polymer deformability is enhanced due to its low viscosity and is increased by an inner pressure from confinement of the polymer flow. Various millimeter-scale polymer structures with high aspect ratios and complex features were hot embossed. In addition, typical microstructures were achieved. This new approach promises the advantages of a broad process capability and strong compatibility with conventional hot embossing processes.

Improvement of photon extraction efficiency of GaN-based LED using micro and nano complex polymer structures

A micro- and nanoscale complex structure made of a high refractive index polymer (n = 2.08) was formed on the ITO electrode layer of an edge-emitting type GaN blue light-emitting diode (LED), in order to improve the photon extraction efficiency by suppressing total internal reflection of photons. The nanoimprint lithography process was used to form the micro- and nanoscale complex structures, using a polymer resin with dispersed TiO2 nano-particles as an imprint resin. Plasma processing, such as reactive ion etching, was used to form the micro- and nano-scale complex structure; thus, plasma-induced damage to the LED device can be avoided. Due to the high refractive index polymeric micro- and nanostructure on the ITO layer, the electroluminescence emission was increased up to 20%, compared to an identical LED that was grown on a patterned sapphire substrate to improve photon extraction efficiency.

Structural Diversity in a Series of Alkyl-Substituted Cesium Aryloxides

A family of cesium aryloxides [Cs(OAr)](n) were synthesized and structurally characterized from the reaction of 1:1 or 1:excess stoichiometry of Cs(0) and the appropriate alkyl-substituted phenol: 2-alkylphenol [alkyl = methyl (H-oMP), isopropyl (H-oPP), and tert-butyl (H-oBP)] and 2,6-dialkylphenol [alkyl = methyl (H-DMP), isopropyl (H-DIP), tert-butyl (H-DBP), and phenyl (H-DPhP)]. The products were structurally identified as [Cs(oMP)(H-oMP)(2)](n) (1), [Cs(5)(oPP)(5)](n) (2), [Cs(4)(oBP)(4)(H-oBP)(6)](n) (3x, shown), [Cs(3)(DMP)(3)](n) (4), [Cs(2)(DIP)(2)](n) (5), [Cs(DIP)(H-DIP)](n) (5x), and [Cs(DPhP)](n) (7). Compounds 1-7 were found to adopt complex polymeric structures employing π interactions from the neighboring pendant phenoxide ligands. The solution behavior of these compounds was studied using solution (133)Cs NMR spectroscopy, and for each compound, a single (133)Cs NMR resonance was observed, with chemical shift values found to be strongly solvent-dependent. This implies that monomeric cesium salt species involving solvent interactions exist in solution.

Application of TOF‐SIMS to the direct determination of syringyl to guaiacyl (S/G) ratio of lignin

AbstractThe lignin syringyl to guaiacyl (S/G) ratio, the composition of monomeric units, is an important parameter that is widely used to obtain information on the complex polymer structure of lignin present in plant cell walls. We assessed the reliability of time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) for determining the S/G ratio using monomer, dimer and polymer model compounds of lignin. In the case of the monomer and dimer, the S/G ratios were much higher than the actual molar S/G ratios. In contrast, for the aryl ether 8‐O‐4′‐linked polymers, the S/G ratios estimated were similar to the actual S/G molar ratios, suggesting that the ionization efficiencies of the characteristic ions of S and G units detected from the synthetic lignin polymer compounds were similar. The results suggest that TOF‐SIMS is useful for rapid and convenient determination of the lignin S/G ratio in plants. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of ageing conditions and block copolymer concentration on the stability and micellization of P123-Ti4+ sols prepared by the templating method

In the work reported here we studied, for the first time, the effects of ageing conditions (temperature and time) on the stability and micellization of two sets of sols with different P123 block copolymer (BC) concentrations by use of dynamic light scattering (DLS). Further, for a comparative study the aggregation/clustering behavior of pure P123 in IPA solution was also examined by DLS, and 1H NMR, and Raman spectroscopy at room temperature. Different ageing regimes applied to the samples prepared included: (i) in-situ ageing of the sols in the sealed capillary cell of the DLS system at room temperature for 0, 1, 2, 3, 4, 5, 6, and 19 h, (ii) ageing of the sols in a Teflon-lined sealed vessel at 50, 55, 60, and 65 °C for 30 min, and (iii) isothermal ageing of the synthesized sols at 50 °C for 1, 4, 8, and 14 days. On the basis of the results obtained it is shown that both ageing time and temperature have remarkable effects on the clustering and aggregation of unimer/micelles formed in the sol system studied. Further, quantitative analysis of interparticle potential energy carried out for the prepared sol at low concentration confirmed that steric interactions play the major role among the other contributing sources of energy. This is mainly related to the presence of BC and the complex polymer structure formed by acetyl acetone (ACAC). Moreover, on the basis of the calculated stability ratio for this sol, we believe that reaction-limited cluster aggregation (RLCA) is possibly the major governing mechanism. Finally, kinetic and dynamic aspects of the micellar aggregates formed are also discussed in this paper.

Erratum to: A correlation between the optical and mechanical properties of novel polysilane/polysiloxane nanocomposites

Poly(di-n-hexyl)silanes (PDNHS), which are σ-conjugated conductive polymers were synthesized by the conventional Wurtz-type coupling reaction. PDNHS were incorporated into polymer networks obtained by cross-linking vinyl terminated poly(dimethyl)siloxanes and methylhydrosiloxane-dimethylsiloxane copolymers. From the UV spectra of polysilane/polysiloxane composites, it can be derived that direct correlations exist between the structure of the polysiloxane matrix and the conformation of small amounts of added polysilanes. The degree of cross-linking plays an important role to understand the structure of the polysiloxane matrix. In addition, rheological measurements indicate that the mechanical properties and the degree of cross-linking in the PDNHS/polysiloxane composites are directly correlated. This implies that the optical properties of small amounts of added PDNHS can be correlated to the mechanical properties of the surrounding polymer matrix. Furthermore, this correlation confirms that PDNHS are suitable to probe the properties of complex polymeric structures.

Formation of three-dimensional hydrogel multilayers using enzyme-mediated redox chain initiation.

Enzyme-mediated redox chain initiation involving glucose oxidase (GOX) was employed in an iterative solution dip-coating technique to polymerize multiple, three-dimensional hydrogel layers using mild aqueous conditions at ambient temperature and oxygen levels. To the best of our knowledge, sequential enzyme-mediated dip-coating resulting in an interfacial radical chain polymerization and subsequent formation of three-dimensional hydrogel layers has not been previously explored. Conformal, micrometer-scale, uniform poly(ethylene glycol) (PEG)-based hydrogel layers were polymerized within seconds and remained securely associated after incubation in water for 16 weeks. Incorporation of either small molecules (i.e., rhodamine-B acrylate, fluorescein acrylate) or fluorescent nanoparticles into crosslinked hydrogel layers during the polymerization reaction was also achieved. The encapsulation of 0.2 microm-diameter nanoparticles into hydrogels during polymerization of a 2-hydroxyethyl acrylate (HEA)/PEG(575) diacrylate monomer formulation, using the GOX-mediated initiation, resulted in minimal effects on polymerization kinetics, with final acrylate conversions of 95% (+/- 1%) achieved within minutes. The temporal control and spatial localization afforded by this interfacial redox approach resulted in the polymerization of uniform secondary layers ranging between 150 (+/- 10) microm and 650 (+/- 10) microm for 15 and 120 s immersion times, respectively. Moreover, increasing the PEG(575)-fraction within the initial hydrogel substrate from 10 to 50% decreased the subsequent layer thicknesses from 690 (+/- 30) microm to 490 (+/- 10) microm because of lowered glucose concentration at the hydrogel interface. The ability to sequentially combine differing initiation mechanisms with this coating approach was achieved by using GOX-mediated interfacial polymerization on hydrogel substrates initially photopolymerized in the presence of glucose. The strict control of layer thicknesses combined with the rapid, water-soluble, and mild polymerization will readily benefit applications requiring formation of stratified, complex, and three-dimensional polymer structures.

Recent Progress in Polyphosphoesters: From Controlled Synthesis to Biomedical Applications

Polyphosphoesters (PPEs) with repeating phosphoester bonds in the backbone are structurally versatile, biocompatible, and biodegradable through hydrolysis as well as enzymatic digestion under physiological conditions. They are appealing for biological applications because of their potential functionality, biocompatibility, and similarity to biomacromolecules such as nucleic acids. The expanding scope of PPEs in materials science, especially as biomaterials, is described in this review. We mainly focus on controlled synthetic methods of PPEs, which provide access to novel and complex polymer structures, especially for block copolymers. The hydrolytic and enzymatic degradation of PPEs, thermoresponsive PPEs, and biomedical applications have also been discussed.

Sickle Hemoglobin Fiber Growth Rates Deduced Using Optical Channels

Sickle hemoglobin (HbS) is a point mutant of normal HbA, and will polymerize at concentrations above a well defined solubility. Polymerization occurs by a double nucleation mechanism in which homogeneous nuclei form in solution following a stochastic delay, and heterogeneous nuclei form on other polymers nucleated by either pathway. A fundamental element is the growth of individual fibers, whose diameter (20 nm) precludes direct optical visualization. Fiber growth and depolymerization have been measured by DIC microscopy, but the heterogeneous pathway makes it possible that bundles rather than single fibers have been observed, in addition to certain technical problems that make interpretation of the results less than simple. We have devised a method in which optical patterns are projected on a COHbS solution by laser photolyis, which creates deoxyHbS that can polymerize only in the illuminated area, easily allowing complex polymer structures to be created optically. In our experiment, polymers first form in an incubation circle. From the circle, a line of deoxyHbS is optically generated along which fibers can grow. Finally, a detection circle is illuminated and the connecting line is extinguished. If a polymer has entered the detection circle, thanks to heterogeneous nucleation it will fill the circle with easily observed polymers, otherwise the detection circle remains monomeric until, at some much later time, homogeneous nucleation occurs. Thus we can measure the elongation of a fiber too small to detect optically. Our preliminary results find growth rates greater than previously observed by DIC microscopy. We can also measure the growth rate of bundles by observing a mass of fibers that subsequently grow along the channel, and these grow at rates comparable to those determined by DIC microscopy. Implications of the measurements and the method will be discussed.

Investigation of Mechanisms of Polycyclic Aromatic Hydrocarbons (PAHs) Initiated from the Thermal Degradation of Styrene Butadiene Rubber (SBR) in N2 Atmosphere

This study has been carried out to characterize the thermal decomposition of styrene-butadiene rubber (SBR), using thermogravimetric analysis (TGA) coupled to online GC/MS, and to investigate the formation and ultimate fate of chemical species produced during gasification of SBR. A preliminary mechanistic understanding has been developed to explain the formation and relationship of light hydrocarbons (C1-C4), substituted aromatics, and polycyclic aromatic hydrocarbons (PAHs) during the decomposition of SBR in a N2 atmosphere. Identification and absolute concentrations of over 50 major and minor species (from hydrogen to benzo[ghi]perylene) have been established, and the measurements have been carried out between 300 and 500 at 10 degrees C/min heating rate in a N2 atmosphere. The concentration of styrene reached 120 PPMV and the concentration of other substituted aromatics, such as toluene and ethyl benzene reached 20 and 5 PPMV, respectively. These measurements indicate PAH formation at a relatively lower temperature as compared to conventional fuel, such as coal and diesel. The PAH sequence is not simply the constructing of larger PAHs from smaller ones to achieve the complex polymer structures. It is possible to generate large PAH molecules while circumventing the typical construction pathway.

Mechanisms of molecular product and persistent radical formation from the pyrolysis of hydroquinone

Hydroquinone is considered to be one of the major, potential molecular precursors for semiquinone-type radicals in the combustion of complex polymeric and oligomeric structures contained in biomass materials. Comprehensive product yield determinations from the high-temperature, gas-phase pyrolysis of hydroquinone in two operational modes (rich and lean hydrogen conditions) are reported at a reaction time of 2.0 s over a temperature range of 250–1000 °C. Below 500 °C, p-benzoquinone is the dominant product, while at temperatures above 650 °C other products including phenol, benzene, styrene, indene, naphthalene, biphenylene, phenylethyne, dibenzofuran and dibenzo- p-dioxin are formed. Hydrogen-rich conditions initially inhibit hydroquinone decomposition (below 500 °C) but promote product formation at higher temperatures. The decomposition process apparently proceeds via formation of a resonance stabilized p-semiquinone radical. Detailed mechanisms of formation of stable molecular species as well as stable radicals are proposed.

New poly(acrylic acid) containing segmented copolymer structures by combination of “click” chemistry and atom transfer radical polymerization

In this paper, the combination of atom transfer radical polymerization (ATRP) of 1-ethoxyethyl acrylate (EEA) and the copper(I) catalyzed “click” 1,3-dipolar cycloaddition reaction of azides and terminal alkynes was evaluated as a method to synthesize diverse amphiphilic copolymer structures. Using the 1-ethoxyethyl protecting group strategy, the application field was broadened with the synthesis of complex polymer structures containing poly(acrylic acid) (PAA) segments. A modular approach has been used: polymers with alkyne functionalities as well as azide functionalities have been synthesized. These polymers were subsequently “clicked” together to yield block copolymers. Furthermore, graft copolymers were synthesized by grafting alkyne-containing polymers onto a polymer backbone with multiple azide functions using the combination of ATRP and “click” reactions.

Clicking polymers: a straightforward approach to novel macromolecular architectures

Living/controlled polymerization techniques have enabled the synthesis of a large variety of different well-defined (co)polymer structures. In addition, the use of click chemistry in polymer science is a quickly emerging field of research since it allows the fast and simple creation of well-defined and complex polymeric structures in yields that were previously unattainable. In this critical review, the application of the azide-alkyne 1,3-dipolar cycloaddition for the construction of well-defined polymer architectures will be discussed in detail, providing a comprehensive overview for all disciplines related to polymeric materials.

From Fundamentals to Applications: Living Polymer Science at the 29th Australasian Polymer Symposium

The previous 28thAustralasian Polymer Symposium in Rotorua, New Zealand, was particularly notable for its elegant fusion of polymer science with biomaterials. As co-Chairs Greg Russell and Martina Stenzel put it in their foreword[1] to the corresponding special issue of the Australian Journal of Chemistry: ‘We must embrace the important challenges posed by the frontier between polymers and biomaterials, for the better future of the world depends on it.’ Although this notion was retained in the conference program of the recent 29th Australasian Polymer Symposium (APS) held in Hobart in February this year, it is notable that the current research and funding culture is permeated with a strong application focus on the biomaterials/ synthetic polymer frontier and the need (or pressure?) to generate immediateand short-term benefits for society. This is also evidenced by an inflation of ‘nano/bio’buzz words in the titles of journal articles as well as funding applications.While an application focus is highly important, great care has to be taken that more fundamental questions also continue to be addressed: after all, the fusion of biological with synthetic polymer science can only advance and benefit immediate applications when the underpinning polymerization processes are fully understood. It is an often overlooked fact that access to the kinetics and mechanism of a polymerization process are key to predicting and controlling polymer microstructures and functionality as well as the design of improved polymerization protocols for accessing well-defined and complex polymer structures. Thus, the main message, which is evident in the current resulting special issue, is that applications and fundamental investigations must support each other. The application-driven fusion of biological aims with synthetic polymer science is highlighted in the current special issue by several articles: a review on the design of star polymer systems and their application in drug delivery[2] contributed by Greg Qiao and James Wiltshire (one of the 29th APS Treloar Prize[3] winners); a focus article on flexible honeycomb-structured films that can be employed in biological contexts (from the second Treloar Prize winner Luke Connal),[4] while a further review

Complex and useful polymer micro- and nanostructures via nanoimprint lithography

This paper presents an overview on three major fabrication techniques developed in our laboratory for achieving complex polymeric structures using nanoimprint lithography (NIL), namely reversal imprinting, combinatorial-mold imprinting and sequential imprinting The key strategy employed by all three techniques is the use of conventional two-dimensional (2D) molds to achieve greater degrees of complexity than are ordinarily achievable with conventional imprinting techniques. For example, reversal imprinting combined with colloidal self-assembly allows for structures that have variations with depth as well as scale. Combinatorial-mold imprinting enables the fabrication of three-dimensional (3D) structures that have variations in length, width as well as depth. Sequential imprinting enables hierarchical structures that have scale-dependent variations and complexity. 3D structures, hierarchical structures, and combinations thereof are obtained in fewer processing steps and without the use of a sacrificial component or process.

Polymeric silver(I) and mercury(II) complexes with chiral bis(pyridyl) ligands

The racemic binaphthol derivatized ligands LL= rac−1,1′-C 20H 12(OCH 2-4-C 5H 4N) 2, 1, and rac−1,1′-C 20H 12(OCH 2-3-C 5H 4N) 2, 2, react with silver trifluoroacetate or with mercury(II) salts to give the polymeric complexes [Ag(O 2CCF 3)(μ-LL)] n or [HgX 2(μ-LL)] n . Individual polymer chains may be chiral or racemic, with sequences of binaphthyl groups with chirality …RRR…, …SSS… or …RSRS…, respectively. The polymer chains may associate, through Ag⋯Ag or Hg–X⋯Hg secondary bonding, to give more complex double-stranded polymer or sheet structures.

Selective electroless plating to fabricate complex three-dimensional metallic micro/nanostructures

We report on selective metal deposition over complex polymer structures formed by two-photon induced photopolymerization technique. Periodic three-dimensional micro/nanostructures are fabricated by means of a microlens array to produce multiple spots from a single-beam femtosecond laser. An electroless plating method is used to deposit a thin silver film onto the sample surface. The glass slide surface supporting the structures is chemically modified to avoid silver coating of the substrate. Our technique enables to produce complex metallic structures with arbitrary shapes under ambient conditions.