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Polymers, Volume 5, Issue 2 (June 2013), Pages 328-872

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Research

Jump to: Review

Open AccessArticle Energetic and Entropic Contributions to the Landau–de Gennes Potential for Gay–Berne Models of Liquid Crystals
Polymers 2013, 5(2), 328-343; doi:10.3390/polym5020328
Received: 15 February 2013 / Revised: 15 March 2013 / Accepted: 19 March 2013 / Published: 27 March 2013
Cited by 5 | PDF Full-text (312 KB) | HTML Full-text | XML Full-text
Abstract
The Landau–de Gennes theory provides a successful macroscopic description of nematics. Cornerstone of this theory is a phenomenological expression for the effective free energy as a function of the orientational order parameter. Here, we show how such a macroscopic Landau–de Gennes free [...] Read more.
The Landau–de Gennes theory provides a successful macroscopic description of nematics. Cornerstone of this theory is a phenomenological expression for the effective free energy as a function of the orientational order parameter. Here, we show how such a macroscopic Landau–de Gennes free energy can systematically be constructed for a microscopic model of liquid crystals formed by interacting mesogens. For the specific example of the Gay–Berne model, we obtain an enhanced free energy that reduces to the familiar Landau–de Gennes expression in the limit of weak ordering. By carefully separating energetic and entropic contributions to the free energy, our approach reconciles the two traditional views on the isotropic–nematic transition of Maier–Saupe and Onsager, attributing the driving mechanism to attractive interactions and entropic effects, respectively. Full article
(This article belongs to the Special Issue Multiscale Simulations in Soft Matter)
Open AccessArticle Esterification of Condensed Tannins and Their Impact on the Properties of Poly(Lactic Acid)
Polymers 2013, 5(2), 344-360; doi:10.3390/polym5020344
Received: 25 February 2013 / Revised: 6 March 2013 / Accepted: 11 April 2013 / Published: 19 April 2013
Cited by 12 | PDF Full-text (434 KB) | HTML Full-text | XML Full-text
Abstract
Reported is a study evaluating the potential of esterified tannins as plastic additives in poly(lactic acid) (PLA). Tannin esterification using anhydrides was investigated as a route to synthesize tannin esters possessing varying ester chain length and degree of substitution (DS). Esterification decreased [...] Read more.
Reported is a study evaluating the potential of esterified tannins as plastic additives in poly(lactic acid) (PLA). Tannin esterification using anhydrides was investigated as a route to synthesize tannin esters possessing varying ester chain length and degree of substitution (DS). Esterification decreased the tannin UV absorbance, predominately in the UVB region. However, tannin materials with longer ester chain lengths exhibited melt behaviors suitable for processing in plastics. On compounding into PLA, tannin hexanoate esters lowered the PLA glass transition by 5–6 °C. Shorter chain length tannin esters had a reduced effect on PLA polymer properties. The PLA flexural properties were significantly altered with stiffness decreases of up to 15% depending on ester chain length and loading. Artificial weathering of modified the PLA samples suggests the presence of tannin esters may confer a protection role to PLA on extended exposure. Overall, results suggest scope for the use of tannin esters possessing longer ester chain length as plastic additives. Full article
(This article belongs to the Special Issue Polymers from Biomass)
Open AccessArticle Cholesterol-Induced Buckling in Physisorbed Polymer-Tethered Lipid Monolayers
Polymers 2013, 5(2), 404-417; doi:10.3390/polym5020404
Received: 29 March 2013 / Accepted: 18 April 2013 / Published: 26 April 2013
Cited by 1 | PDF Full-text (1690 KB) | HTML Full-text | XML Full-text
Abstract
The influence of cholesterol concentration on the formation of buckling structures is studied in a physisorbed polymer-tethered lipid monolayer system using epifluorescence microscopy (EPI) and atomic force microscopy (AFM). The monolayer system, built using the Langmuir-Blodgett (LB) technique, consists of 3 mol [...] Read more.
The influence of cholesterol concentration on the formation of buckling structures is studied in a physisorbed polymer-tethered lipid monolayer system using epifluorescence microscopy (EPI) and atomic force microscopy (AFM). The monolayer system, built using the Langmuir-Blodgett (LB) technique, consists of 3 mol % poly(ethylene glycol) (PEG) lipopolymers and various concentrations of the phospholipid, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), and cholesterol (CHOL). In the absence of CHOL, AFM micrographs show only occasional buckling structures, which is caused by the presence of the lipopolymers in the monolayer. In contrast, a gradual increase of CHOL concentration in the range of 0–40 mol % leads to fascinating film stress relaxation phenomena in the form of enhanced membrane buckling. Buckling structures are moderately deficient in CHOL, but do not cause any notable phospholipid-lipopolymer phase separation. Our experiments demonstrate that membrane buckling in physisorbed polymer-tethered membranes can be controlled through CHOL-mediated adjustment of membrane elastic properties. They further show that CHOL may have a notable impact on molecular confinement in the presence of crowding agents, such as lipopolymers. Our results are significant, because they offer an intriguing prospective on the role of CHOL on the material properties in complex membrane architecture. Full article
(This article belongs to the Special Issue Polymer Thin Films and Membranes 2013)
Open AccessArticle One-Dimensional Coordination Polymers of Lanthanide Cations to Cucurbit[7]uril Built Using a Range of Tetrachloride Transition-Metal Dianion Structure Inducers
Polymers 2013, 5(2), 418-430; doi:10.3390/polym5020418
Received: 18 March 2013 / Revised: 30 April 2013 / Accepted: 3 May 2013 / Published: 16 May 2013
Cited by 18 | PDF Full-text (4333 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A number of linear coordination polymers have been assembled from lanthanide cations (Ln3+) and cucurbit[7]uril (Q[7]) in the presence of [CuCl4]2−or [CoCl4]2− anions acting as inorganic structure inducers in HCl solution. X-ray diffraction [...] Read more.
A number of linear coordination polymers have been assembled from lanthanide cations (Ln3+) and cucurbit[7]uril (Q[7]) in the presence of [CuCl4]2−or [CoCl4]2− anions acting as inorganic structure inducers in HCl solution. X-ray diffraction analysis has revealed that they form three groups of isomorphous structures. Generally, the complexes of Q[7] with light lanthanide cations (those with atomic number below that of neodymium (Nd3+)) are in one group. The other two groups, in which the lanthanide cation has atomic number greater than that of europium (Eu3+), seem to follow no obvious rule. For example, the complexes of Q[7] with Eu3+ and Gd3+cations are in the second group in the presence of [CuCl4]2− anions, while they are in the third group in the presence of [CoCl4]2− anions. However, whatever group a given complex belongs to, they all show a common honeycomb-patterned supramolecular assembly, in which [CuCl4]2−or [CoCl4]2− anions form a honeycomb structure. The Ln3+ cations then coordinate to neighboring Q[7] molecules to form 1D coordination polymers that are inserted into the channels of the honeycomb framework, such that each individual coordination polymer is surrounded by [CuCl4]2−or [CoCl4]2− anions. Full article
(This article belongs to the Special Issue Supramolecular Chemistry and Self-Assembly)
Open AccessArticle Fluctuating Entanglements in Single-Chain Mean-Field Models
Polymers 2013, 5(2), 643-678; doi:10.3390/polym5020643
Received: 22 March 2013 / Revised: 9 May 2013 / Accepted: 20 May 2013 / Published: 3 June 2013
Cited by 10 | PDF Full-text (489 KB) | HTML Full-text | XML Full-text
Abstract
We consider four criteria of acceptability for single-chain mean-field entangled polymer models: consistency with a multi-chain level of description, consistency with nonequilibrium thermodynamics, consistency with the stress-optic rule, and self-consistency between Green–Kubo predictions and linear viscoelastic predictions for infinitesimally driven systems. Each [...] Read more.
We consider four criteria of acceptability for single-chain mean-field entangled polymer models: consistency with a multi-chain level of description, consistency with nonequilibrium thermodynamics, consistency with the stress-optic rule, and self-consistency between Green–Kubo predictions and linear viscoelastic predictions for infinitesimally driven systems. Each of these topics has been considered independently elsewhere. However, we are aware of no molecular entanglement model that satisfies all four criteria simultaneously. Here we show that an idea from Ronca and Allegra, generalized to arbitrary flows, can be implemented in a slip-link model to create a model that does satisfy all four criteria. Aside from the direct benefits of agreement, the result modifies the relation between the initial relaxation modulus G(0) and the entanglement molecular weight Me. If this implementation is correct, current estimates for Me would require modification that brings their values more in line with estimates based on topological analysis of molecular dynamics simulations. Full article
(This article belongs to the Special Issue Multiscale Simulations in Soft Matter)
Open AccessArticle Supramolecular Assemblies from Poly(styrene)-block-poly(4-vinylpyridine) Diblock Copolymers Mixed with 6-Hydroxy-2-naphthoic Acid
Polymers 2013, 5(2), 679-695; doi:10.3390/polym5020679
Received: 14 April 2013 / Revised: 22 May 2013 / Accepted: 28 May 2013 / Published: 5 June 2013
Cited by 7 | PDF Full-text (3237 KB) | HTML Full-text | XML Full-text
Abstract
Supramolecular assemblies involving interaction of a small organic molecule, 2-hydroxy-6-Naphthoic acid (HNA), with poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers are utilized to obtain micellar structures in solution, nanostructured thin films on flat substrates and, finally, nanoporous thin films. The formation [...] Read more.
Supramolecular assemblies involving interaction of a small organic molecule, 2-hydroxy-6-Naphthoic acid (HNA), with poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers are utilized to obtain micellar structures in solution, nanostructured thin films on flat substrates and, finally, nanoporous thin films. The formation of hydrogen bonds between HNA and the poly(4-vinylpyridine) (P4VP) blocks is confirmed by spectroscopic measurements. The accordingly P4VP/HNA hydrogen-bonded complexes are poorly soluble in 1,4-dioxane, resulting in the formation of micellar structures with a P4VP/HNA core and a polystyrene (PS) corona. Those micelles have been spin-coated onto silicon wafers, resulting in nanostructured thin films consisting of P4VP/HNA dot-like features embedded in a PS matrix. The morphology of those films has been tuned by solvent annealing. Selective dissolution of HNA by methanol results in the formation of a nanoporous thin film. The P4VP/HNA nanodomains have been also cross-linked by borax, and the thin films have been further dissolved in a good solvent for PS, leading to micelles with a structure reminiscent of the thin films. Full article
(This article belongs to the Special Issue Non-Equilibrium Blockcopolymer Self-Assembly)
Open AccessArticle Ion Permeability of Free-Suspended Layer-by-Layer (LbL) Films Prepared Using an Alginate Scaffold
Polymers 2013, 5(2), 696-705; doi:10.3390/polym5020696
Received: 26 March 2013 / Revised: 9 May 2013 / Accepted: 3 June 2013 / Published: 6 June 2013
Cited by 2 | PDF Full-text (293 KB) | HTML Full-text | XML Full-text
Abstract
Layer-by-layer (LbL) films were prepared over an aperture (diameter 1–5 mm) on a glass plate to study ion permeation across free-suspended LbL films. LbL films were prepared by depositing alternating layers of poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on the surface [...] Read more.
Layer-by-layer (LbL) films were prepared over an aperture (diameter 1–5 mm) on a glass plate to study ion permeation across free-suspended LbL films. LbL films were prepared by depositing alternating layers of poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on the surface of a glass plate with an aperture filled with an alginate gel, followed by dissolution of the alginate gel. PAH-PSS films prepared in this way showed permeability to inorganic salts, depending on the size and charge. Permeability to alkali metal chlorides depended on the Stokes radius of the alkali metal cations. The effect of the type of halide was negligible because of the halides’ smaller ionic radii. Permeation of multivalent ions such as Ru(NH3)63+ and [Fe(CN)6]3 was severely suppressed owing to Donnan exclusion. Full article
(This article belongs to the Special Issue Polymer Thin Films and Membranes 2013)
Open AccessArticle Photocrosslinkable Star Polymers via RAFT-Copolymerizations with N-Ethylacrylate-3,4-dimethylmaleimide
Polymers 2013, 5(2), 706-729; doi:10.3390/polym5020706
Received: 25 April 2013 / Revised: 30 May 2013 / Accepted: 30 May 2013 / Published: 10 June 2013
Cited by 7 | PDF Full-text (1106 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper describes the Z-RAFT-star copolymerization of n-butyl acrylate (BA) and N-isopropyl acrylamide (NIPAm), respectively, with N-ethylacrylate-3,4-dimethylmaleimide (1.1), a monomer carrying a UV-reactive unit that undergoes photocrosslinking. Addition of 1.1 slows down the polymerization rate both for [...] Read more.
This paper describes the Z-RAFT-star copolymerization of n-butyl acrylate (BA) and N-isopropyl acrylamide (NIPAm), respectively, with N-ethylacrylate-3,4-dimethylmaleimide (1.1), a monomer carrying a UV-reactive unit that undergoes photocrosslinking. Addition of 1.1 slows down the polymerization rate both for BA and for NIPAm polymerization. Double star formation due to radical attack to the 3,4-dimethylmaleimide moiety was found in the case of BA. Dead polymer formation, presumably due to aminolysis as side-reaction, was pronounced in the NIPAm system. These two effects broadened the molar mass distributions, but did not impede the formation of functional star polymers. The composition of the copolymers as well as the reactivity ratios for the applied comonomers were determined via NMR spectroscopy (BA-co-1.1 r1.1 = 2.24 rBA = 0.95; NIPAm-co-1.1 r1.1 = 0.96 rNIPAm = 0.05). In both cases, the comonomer is consumed preferably in the beginning of the polymerization, thus forming gradient copolymer stars with the UV-reactive units being located in the outer sphere. Full article
(This article belongs to the Special Issue Complex Macromolecular Architectures)
Open AccessArticle A Multiscale Mechanical Model for Plant Tissue Stiffness
Polymers 2013, 5(2), 730-750; doi:10.3390/polym5020730
Received: 1 April 2013 / Revised: 10 May 2013 / Accepted: 13 May 2013 / Published: 10 June 2013
Cited by 4 | PDF Full-text (23476 KB) | HTML Full-text | XML Full-text
Abstract
Plant petioles and stems are hierarchical cellular structures, displaying structuralfeatures defined at multiple length scales. The current work focuses on the multi-scalemodelling of plant tissue, considering two orders of structural hierarchy, cell wall and tissue.The stiffness of plant tissue is largely governed [...] Read more.
Plant petioles and stems are hierarchical cellular structures, displaying structuralfeatures defined at multiple length scales. The current work focuses on the multi-scalemodelling of plant tissue, considering two orders of structural hierarchy, cell wall and tissue.The stiffness of plant tissue is largely governed by the geometry of the tissue cells, thecomposition of the cell wall and the structural properties of its constituents. The cell wallis analogous to a fiber reinforced composite, where the cellulose microfibril (CMF) is theload bearing component. For multilayered cell wall, the microfibril angle (MFA) in themiddle layer of the secondary cell wall (S2 layer) largely affects the longitudinal stiffnessfor values up to 40o. The MFA in turn influences the overall wall stiffness. In this work,the effective stiffness of a model system based on collenchyma cell wall of a dicotyledonousplant, the Rheum rhabarbarum, is computed considering generic MFA and volume fractions.At the cellular level, a 2-D Finite Edge Centroidal Voronoi tessellation (FECVT) has beendeveloped and implemented to generate the non-periodic microstructure of the plant tissue.The effective elastic properties of the cellular tissue are obtained through finite elementanalysis (FEA) of the Voronoi model coupled with the cell wall properties. The stiffness ofthe hierarchically modeled tissue is critically important in determining the overall structuralproperties of plant petioles and stems. Full article
(This article belongs to the Special Issue Multiscale Simulations in Soft Matter)
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Open AccessArticle Solid-State Organization and Ambipolar Field-Effect Transistors of Benzothiadiazole-Cyclopentadithiophene Copolymer with Long Branched Alkyl Side Chains
Polymers 2013, 5(2), 833-846; doi:10.3390/polym5020833
Received: 15 April 2013 / Revised: 15 May 2013 / Accepted: 16 May 2013 / Published: 18 June 2013
Cited by 8 | PDF Full-text (969 KB) | HTML Full-text | XML Full-text
Abstract
The solid-state organization of a benzothiadiazole-cyclopentadithiophene copolymer with long, branched decyl-tetradecyl side chains (CDT-BTZ-C14,10) is investigated. The C14,10 substituents are sterically demanding and increase the π-stacking distance to 0.40 nm from 0.37 nm for the same polymer with linear [...] Read more.
The solid-state organization of a benzothiadiazole-cyclopentadithiophene copolymer with long, branched decyl-tetradecyl side chains (CDT-BTZ-C14,10) is investigated. The C14,10 substituents are sterically demanding and increase the π-stacking distance to 0.40 nm from 0.37 nm for the same polymer with linear hexadecyls (C16). Despite the bulkiness, the C14,10 side chains tend to crystallize, leading to a small chain-to-chain distance between lamellae stacks and to a crystal-like microstructure in the thin film. Interestingly, field-effect transistors based on solution processed layers of CDT-BTZ-C14,10 show ambipolar behavior in contrast to CDT-BTZ-C16 with linear side chains, for which hole transport was previously observed. Due to the increased π-stacking distance, the mobilities are only 6 × 104 cm²/Vs for electrons and 6 × 105 cm²/Vs for holes, while CDT-BTZ-C16 leads to values up to 5.5 cm²/Vs. The ambipolarity is attributed to a lateral shift between stacked backbones provoked by the bulky C14,10 side chains. This reorganization is supposed to change the transfer integrals between the C16 and C14,10 substituted polymers. This work shows that the electronic behavior in devices of one single conjugated polymer (in this case CDT-BTZ) can be controlled by the right choice of the substituents to place the backbones in the desired packing. Full article
(This article belongs to the Special Issue Supramolecular Chemistry and Self-Assembly)
Open AccessArticle Progress in Imidazolium Ionic Liquids Assisted Fabrication of Carbon Nanotube and Graphene Polymer Composites
Polymers 2013, 5(2), 847-872; doi:10.3390/polym5020847
Received: 15 April 2013 / Revised: 31 May 2013 / Accepted: 4 June 2013 / Published: 21 June 2013
Cited by 24 | PDF Full-text (728 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanotubes (CNTs) and graphene sheets are the most promising fillers for polymer nanocomposites due to their superior mechanical, electrical, thermal optical and gas barrier properties, as well as high flame-retardant efficiency. The critical challenge, however, is how to uniformly disperse them [...] Read more.
Carbon nanotubes (CNTs) and graphene sheets are the most promising fillers for polymer nanocomposites due to their superior mechanical, electrical, thermal optical and gas barrier properties, as well as high flame-retardant efficiency. The critical challenge, however, is how to uniformly disperse them into the polymer matrix to achieve a strong interface for good load transfer between the two. This problem is not new but more acute in CNTs and graphene, both because they are intrinsically insoluble and tend to aggregate into bundles and because their surfaces are atomically smooth. Over the past decade, imidazolium ionic liquids (Imi-ILs) have played a multifunctional role (e.g., as solvents, dispersants, stabilizers, compatibilizers, modifiers and additives) in the fabrication of polymer composites containing CNTs or graphene. In this review, we first summarize the liquid-phase exfoliation, stabilization, dispersion of CNTs and graphene in Imi-ILs, as well as the chemical and/or thermal reduction of graphene oxide to graphene with the aid of Imi-ILs. We then present a full survey of the literature on the Imi-ILs assisted fabrication of CNTs and graphene-based nanocomposites with a variety of polymers, including fluoropolymers, hydrocarbon polymers, polyacrylates, cellulose and polymeric ionic liquids. Finally, we give a future outlook in hopes of facilitating progress in this emerging area. Full article

Review

Jump to: Research

Open AccessReview Ring-Opening Polymerization—An Introductory Review
Polymers 2013, 5(2), 361-403; doi:10.3390/polym5020361
Received: 21 March 2013 / Revised: 9 April 2013 / Accepted: 10 April 2013 / Published: 25 April 2013
Cited by 42 | PDF Full-text (1491 KB) | HTML Full-text | XML Full-text
Abstract
This short, introductory review covers the still rapidly growing and industrially important field of ring opening polymerization (ROP). The review is organized according to mechanism (radical ROP (RROP), cationic ROP (CROP), anionic ROP (AROP) and ring-opening metathesis polymerization (ROMP)) rather than monomer [...] Read more.
This short, introductory review covers the still rapidly growing and industrially important field of ring opening polymerization (ROP). The review is organized according to mechanism (radical ROP (RROP), cationic ROP (CROP), anionic ROP (AROP) and ring-opening metathesis polymerization (ROMP)) rather than monomer classes. Nevertheless, the different groups of cyclic monomers are considered (olefins, ethers, thioethers, amines, lactones, thiolactones, lactams, disulfides, anhydrides, carbonates, silicones, phosphazenes and phosphonites) and the mechanisms by which they can be polymerized involving a ring-opening polymerization. Literature up to 2012 has been considered but the citations selected refer to detailed reviews and key papers, describing not only the latest developments but also the evolution of the current state of the art. Full article
(This article belongs to the Special Issue Ring-Opening Polymerization)
Open AccessReview Synthesis of Glycopolymer Architectures by Reversible-Deactivation Radical Polymerization
Polymers 2013, 5(2), 431-526; doi:10.3390/polym5020431
Received: 22 March 2013 / Revised: 1 May 2013 / Accepted: 3 May 2013 / Published: 21 May 2013
Cited by 23 | PDF Full-text (2913 KB) | HTML Full-text | XML Full-text
Abstract
This review summarizes the state of the art in the synthesis of well-defined glycopolymers by Reversible-Deactivation Radical Polymerization (RDRP) from its inception in 1998 until August 2012. Glycopolymers architectures have been successfully synthesized with four major RDRP techniques: Nitroxide-mediated radical polymerization (NMP), [...] Read more.
This review summarizes the state of the art in the synthesis of well-defined glycopolymers by Reversible-Deactivation Radical Polymerization (RDRP) from its inception in 1998 until August 2012. Glycopolymers architectures have been successfully synthesized with four major RDRP techniques: Nitroxide-mediated radical polymerization (NMP), cyanoxyl-mediated radical polymerization (CMRP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. Over 140 publications were analyzed and their results summarized according to the technique used and the type of monomer(s) and carbohydrates involved. Particular emphasis was placed on the experimental conditions used, the structure obtained (comonomer distribution, topology), the degree of control achieved and the (potential) applications sought. A list of representative examples for each polymerization process can be found in tables placed at the beginning of each section covering a particular RDRP technique. Full article
(This article belongs to the Special Issue Bioconjugates/Biohybrid Polymers)
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Open AccessReview Structural Diversity of Metallosupramolecular Assemblies Based on the Bent Bridging Ligand 4,4′-Dithiodipyridine
Polymers 2013, 5(2), 527-575; doi:10.3390/polym5020527
Received: 2 April 2013 / Revised: 30 April 2013 / Accepted: 3 May 2013 / Published: 21 May 2013
Cited by 6 | PDF Full-text (2704 KB) | HTML Full-text | XML Full-text
Abstract
4,4′-Dithiodipyridine (dtdp), also termed 4,4′-dipyridyldisulfide, is a bridging ligand of the 4,4′-bipyridine type. The introduction of the disulfide moiety inevitably leads to a relatively rigid angular structure, which exhibits axial chirality. More than 90 metal complexes containing the dtdp ligand [...] Read more.
4,4′-Dithiodipyridine (dtdp), also termed 4,4′-dipyridyldisulfide, is a bridging ligand of the 4,4′-bipyridine type. The introduction of the disulfide moiety inevitably leads to a relatively rigid angular structure, which exhibits axial chirality. More than 90 metal complexes containing the dtdp ligand have been crystallographically characterised until now. This review focuses on the preparation and structural diversity of discrete and polymeric metallosupramolecular assemblies constructed from dtdp as bridging ligands. These encompass metallamacrocycles with M2L2 topology and coordination polymers with periodicity in one or two dimensions. One-dimensional coordination polymers represent the vast majority of the metallosupramolecular structures obtained from dtdp. These include repeated rhomboids, zigzag, helical and arched chains among other types. In this contribution, we make an attempt to provide a comprehensive account of the structural data that are currently available for metallosupramolecular assemblies based on the bent bridging ligand dtdp. Full article
(This article belongs to the Special Issue Supramolecular Chemistry and Self-Assembly)
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Open AccessReview Polymer Directed Protein Assemblies
Polymers 2013, 5(2), 576-599; doi:10.3390/polym5020576
Received: 1 April 2013 / Revised: 7 May 2013 / Accepted: 8 May 2013 / Published: 22 May 2013
Cited by 19 | PDF Full-text (2078 KB) | HTML Full-text | XML Full-text
Abstract
Protein aggregation and protein self-assembly is an important occurrence in natural systems, and is in some form or other dictated by biopolymers. Very obvious influences of biopolymers on protein assemblies are, e.g., virus particles. Viruses are a multi-protein assembly of which the [...] Read more.
Protein aggregation and protein self-assembly is an important occurrence in natural systems, and is in some form or other dictated by biopolymers. Very obvious influences of biopolymers on protein assemblies are, e.g., virus particles. Viruses are a multi-protein assembly of which the morphology is dictated by poly-nucleotides namely RNA or DNA. This “biopolymer” directs the proteins and imposes limitations on the structure like the length or diameter of the particle. Not only do these bionanoparticles use polymer-directed self-assembly, also processes like amyloid formation are in a way a result of directed protein assembly by partial unfolded/misfolded biopolymers namely, polypeptides. The combination of proteins and synthetic polymers, inspired by the natural processes, are therefore regarded as a highly promising area of research. Directed protein assembly is versatile with respect to the possible interactions which brings together the protein and polymer, e.g., electrostatic, v.d. Waals forces or covalent conjugation, and possible combinations are numerous due to the large amounts of different polymers and proteins available. The protein-polymer interacting behavior and overall morphology is envisioned to aid in clarifying protein-protein interactions and are thought to entail some interesting new functions and properties which will ultimately lead to novel bio-hybrid materials. Full article
(This article belongs to the Special Issue Supramolecular Chemistry and Self-Assembly)
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Open AccessReview Functionalized Polymers from Lignocellulosic Biomass: State of the Art
Polymers 2013, 5(2), 600-642; doi:10.3390/polym5020600
Received: 25 February 2013 / Revised: 12 April 2013 / Accepted: 14 May 2013 / Published: 28 May 2013
Cited by 13 | PDF Full-text (3811 KB) | HTML Full-text | XML Full-text
Abstract
Since the realization that global sustainability depends on renewable sources of materials and energy, there has been an ever-increasing need to develop bio-based polymers that are able to replace petroleum-based polymers. Research in this field has shown strong potential in generating high-performance [...] Read more.
Since the realization that global sustainability depends on renewable sources of materials and energy, there has been an ever-increasing need to develop bio-based polymers that are able to replace petroleum-based polymers. Research in this field has shown strong potential in generating high-performance functionalized polymers from plant biomass. With the anticipated large-scale production of lignocellulosic biomass, lignin, cellulose and hemicellulosic polysaccharides will be abundantly available renewable feedstocks for biopolymers and biocomposites with physico-chemical properties that match or exceed those of petroleum-based compounds. This review examines the state of the art regarding advances and challenges in synthesis and applications of specialty polymers and composites derived from cellulose, hemicellulose and lignin, ending with a brief assessment of genetic modification as a route to tailor crop plants for specific applications. Full article
(This article belongs to the Special Issue Polymers from Biomass)
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Open AccessReview Challenges in Multiscale Modeling of Polymer Dynamics
Polymers 2013, 5(2), 751-832; doi:10.3390/polym5020751
Received: 3 April 2013 / Revised: 16 May 2013 / Accepted: 30 May 2013 / Published: 13 June 2013
Cited by 38 | PDF Full-text (3813 KB) | HTML Full-text | XML Full-text
Abstract
The mechanical and physical properties of polymeric materials originate from the interplay of phenomena at different spatial and temporal scales. As such, it is necessary to adopt multiscale techniques when modeling polymeric materials in order to account for all important mechanisms. Over [...] Read more.
The mechanical and physical properties of polymeric materials originate from the interplay of phenomena at different spatial and temporal scales. As such, it is necessary to adopt multiscale techniques when modeling polymeric materials in order to account for all important mechanisms. Over the past two decades, a number of different multiscale computational techniques have been developed that can be divided into three categories: (i) coarse-graining methods for generic polymers; (ii) systematic coarse-graining methods and (iii) multiple-scale-bridging methods. In this work, we discuss and compare eleven different multiscale computational techniques falling under these categories and assess them critically according to their ability to provide a rigorous link between polymer chemistry and rheological material properties. For each technique, the fundamental ideas and equations are introduced, and the most important results or predictions are shown and discussed. On the one hand, this review provides a comprehensive tutorial on multiscale computational techniques, which will be of interest to readers newly entering this field; on the other, it presents a critical discussion of the future opportunities and key challenges in the multiscale modeling of polymeric materials and how these methods can help us to optimize and design new polymeric materials. Full article
(This article belongs to the Special Issue Multiscale Simulations in Soft Matter)
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