Monodisperse Polymer Research Articles

Self-assembly of monodisperse polymer particles into photonic crystals and incorporation of chromophores in them

Self-assembly of monodisperse polymer particles into photonic crystals and incorporation of chromophores in them

Relaxation time spectrum molecular weight distribution relationships

Single exponential decay \(\exp(-t/\tau)\) relationships, which define the molecular weight distribution (MWD) of a polymer as a function of the polymer’s relaxation time spectrum (RTS), have been derived by Wu (Polym Eng Sci 28:538–543, 1988) and Thimm et al. (J Rheol 43:1663–1672, 1999). Experimental validation studies with monodisperse polymers, with quite precisely known MWDs, have been used to test their reliability. It has been established that neither formula is always able to accurately recover the MWDs of monodisperse polymers from their experimentally determined RTS. In this paper, different and more general relationships, based on theoretical results of Anderssen and Loy (Bull Aust Math Soc 65:449–460, 2002a) for decays of the form \(\exp(-\theta(t)/\tau)\), where the derivative of θ(t) is a completely monotone function, are derived, analyzed, and applied. It is shown how to transform these general relationships to equivalent single exponential decay relationships for which Laplace transform solutions are derived. In order to illustrate the interrelationship between an RTS and its corresponding MWD, an explicit analytic solution is given. The paper concludes with a discussion of the rheological implications for the BSW model.

Facile Fabrication of Monodisperse Polymer Hollow Spheres

This article reports the facile synthesis of monodisperse polymer hollow spheres by seeded emulsion polymerization without additional treatment. In this method, P(St-MMA-MAA) copolymer latex particles were first prepared by emulsifier-free emulsion polymerization and then used as seeds to carry out emulsion polymerization of methyl methacrylate (MMA), divinyl benzene (DVB), and 2-hydroxyethyl methacrylate (HEMA) with potassium persulfate (KPS) as initiator at 80 degrees C. The void of hollow spheres was readily adjusted by changing the monomer/seed weight ratio, and it could be enlarged while the diameters of hollow spheres changed little after etching by dimethyl formamide (DMF). The effects of synthetic parameters including the monomer composition and the properties of seeds on the morphology of hollow spheres were investigated in detail. On the basis of the experimental results, it seemed reasonable to conclude that the formation of hollow spheres was due to the "dissolution" of seeds in monomers and phase separation between the constituent polymers. As a thermodynamic factor, sodium dodecyl sulfate (SDS) would allow the preparation of solid particles depending on its level.

Grafting Monodisperse Polymer Chains from Concave Surfaces of Ordered Mesoporous Silicas

Surface-initiated atom transfer radical polymerization (ATRP) was used to graft uniform layers of polyacrylonitrile (PAN), poly(2-(dimethylamino)ethyl methacrylate), and polystyrene on concave surfaces of cylindrical mesopores of diameter ∼10 nm and spherical mesopores of diameter ∼15 nm. The grafting process was optimized through the introduction of appropriate amounts of Cu(II) species that act as a deactivator, allowing us to grow polymer layers of controlled thickness (as seen from gas adsorption), which consisted of monodisperse polymer chains of controlled molecular weight (as seen from gel permeation chromatography). For PAN, the degrees of polymerization ranged from DP = 25 to 70, and the polydispersity indexes of the polymer grafted under optimal conditions were as low as Mw/Mn = 1.06−1.07. Grafted chain densities up to 0.28 chains/nm2 and initiation efficiencies up to 37% were achieved. In cases of spherical mesopores of diameter ∼15 nm, it was possible to introduce significant loadings of polym...

Preparation of highly monodisperse fluorescent polymer particles by miniemulsion polymerization of styrene with a polymerizable surfactant

Miniemulsion polymerization of styrene (St) in the presence of a hydrophobe (hexadecane:HD) using a cationic polymerizable surfactant ( N , N -dimethyl- N - n -dodecyl- N-2-methacryloyloxyethylammonium bromide:C 12Br) and a cationic initiator (2,2′-azobis(2-amidinopropane) dihydrochloride:V50), called St/C 12Br/V50 hereafter, proceeded efficiently compared with that using sodium dodecyl sulfate (SDS) and potassium persulfate (KPS), i.e., St/SDS/KPS, providing monodisperse polystyrene latex particles with a narrower particle size distribution. In St/C 12Br/AIBN, where an oil-soluble initiator, i.e., 2,2′-azobisisobutyronitrile (AIBN), was used in place of V50, little changes in polymerization kinetics or in particle size distribution were observed, while a significant drop in polymerization rate and a broad particle size distribution were observed with St/SDS/AIBN. A polymerizable pyrene derivative (1-pyrenylmethyl methacrylate: PyMMA) was quantitatively incorporated into monodisperse latex particles in St/PyMMA/C 12Br/V50 compared to pyrene (Py) in St/Py/C 12Br/V50. Contrary to our expectation, however, increased excimer emission was observed with St/PyMMA/C 12Br/V50 particles, indicating less evenly distributed pyrene chromophores in the particles. The fluorescence lifetime of pyrene chromophores in St/Py/C 12Br/V50 particles was determined to be 286 ns, which was 17 times longer than that of pyrene in THF solution.

Surface Instabilities of Monodisperse and Densely Grafted Polymer Brushes

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSurface Instabilities of Monodisperse and Densely Grafted Polymer BrushesHolger Merlitz*†‡, Gui-Li He†, Chen-Xu Wu†, and Jens-Uwe Sommer‡View Author Information Department of Physics and ITPA, Xiamen University, Xiamen 361005, P.R. China, and Leibniz-Institut für Polymerforschung Dresden, D-01069 Dresden, Germany* Corresponding author. E-mail:[email protected]†Department of Physics and ITPA, Xiamen University.‡Leibniz-Institut für Polymerforschung Dresden.Cite this: Macromolecules 2008, 41, 13, 5070–5072Publication Date (Web):June 4, 2008Publication History Received23 January 2008Revised18 April 2008Published online4 June 2008Published inissue 1 July 2008https://doi.org/10.1021/ma800163aCopyright © 2008 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views516Altmetric-Citations36LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (607 KB) Get e-AlertsSUBJECTS:Free energy,Modification,Monomers,Physical and chemical properties,Polymer brushes Get e-Alerts

Relaxation patterns of long, linear, flexible, monodisperse polymers: BSW spectrum revisited

Theoretical predictions for the dynamic mod- uli of long, linear, flexible, monodisperse polymers are summarized and compared with experimental obser- vations. Surprisingly, the predicted 1/2 power scaling of the long-time modes of the relaxation spectrum is not found in the experiments. Instead, scaling with a power of about 1/4 extends all the way up to the longest relaxation times near τ /τmax = 1. This is expressed in the empirical relaxation time spectrum of Baumgaertel- Schausberger-Winter, denoted as "BSW spectrum," and justifies a closer look at the properties of the BSW spectrum. Working with the BSW spectrum, however, is made difficult by the fact that hypergeometric func- tions occur naturally in BSW-based rheological mate- rial functions. BSW provides no explicit solutions for the dynamic moduli, G � (ω), G �� (ω), or the relaxation modulus G(t). To overcome this problem, close ap- proximations of simple analytical form are shown for these moduli. With these approximations, analysis of linear viscoelastic data allows the direct determination of BSW parameters.

Templated Synthesis of Single-Component Polymer Capsules and Their Application in Drug Delivery

We report a general and facile approach for the fabrication of a new class of monodispersed, single-component and thick-walled polymer nanocapsules via the single-step assembly of macromolecules in solid core/mesoporous shell (SC/MS) silica particle templates, followed by cross-linking of the macromolecules and removal of the SC/MS templates. The general applicability of this approach is demonstrated by the preparation of nanocapsules using various polymers, including synthetic polyelectrolytes, polypeptides, and polypeptide-drug conjugates. The potential of doxorubicin (Dox)-loaded poly(L-glutamic acid) nanocapsules in tumor therapy applications is demonstrated via in vitro degradation experiments, which show a near-linear release of the Dox in the presence of a lysosomal hydrolase, nanocapsule uptake by human colorectal tumor cells, and delivery of the anticancer drug into the tumor cells, leading to tumor cell death.

Adhesion at interfaces between highly entangled polymer melts

The failure of interfaces between a series of styrene-butadiene random linear monodisperse polymer melts was investigated with a contact mechanics method. A thin (1μm) and a thick (150μm) film of the same polymer were deposited on a metallic cylindrical probe and on a glass slide, respectively. The two films were put in contact for up to 1000s in a very confined geometry and the mechanical strength of interfaces formed in these conditions was then characterized by separating the probe from the glass slide. We observed different deformation micromechanisms of the layers depending on the time of contact, the debonding velocity, and the polymer used. We found that these different behaviors could be represented in a general deformation map as a function of two reduced parameters: the ratio between the contact time and the reptation time and the Deborah number. For values of De Decrit, two regimes were obse...

Synthesis of Spherical Ultra‐High‐Surface‐Area Monodisperse Amphipathic Polymer Sponges in the Low‐Micrometer Size Range

Spherical, ultra-high specific surface area monodisperse polymer particles with diameters in the low micrometer size range are disclosed for the first time. The polymer particles are able to sorb significant levels of both hydrocarbon solvents and water, acting in effect as amphipathic micro-sponges. Exciting possibilities for exploitation of the particles in chromatography, diagnostics, sensors, delivery vehicles and catalysis are suggested.

Three-Dimensional Hierarchically Organized Magnetic Nanoparticle Polymer Composites: Achievement of Monodispersity and Enhanced Tensile Strength

Synthesis of monodisperse polymer−inorganic nanoparticle composites and the study of their mechanical properties are described. Surface-modified MPt (M = Fe, Ni) nanoparticles undergo hydrosilation reaction with siloxane backbones and make covalent networks by acting as crosslinkers. Monodispersity and the spatial resolution of nanoparticles were identified with atomic force microscopy and transmission electron microscopy. The properties of covalent bonding in the elastomeric network between nanoparticles, allyl-modified dopamine, and siloxane backbones were studied with X-ray photoelectron spectroscopy and IR. The added amount of dopamine-modified FePt nanoparticles affected the crosslinking density in the siloxane backbones. The intensity of Si−H bonding was decreased in IR spectra with increasing density of FePt nanoparticles. Mechanical properties were measured with nanoindentation. FePt nanoparticle polymer composites have more enhanced tensile strength (Er = 1.56 GPa, H = 0.126 GPa) than simple elastomers crosslinked with diallyl carbonate (Er = 0.67 GPa, H = 0.115 GPa). Further improvement of mechanical strength was achieved with increased amount of dopamine-modified nanoparticles due to the increase in the crosslinking density between siloxane backbones.

Preparation of highly cross-linked monodispersed functional polystyrene particles by utilizing the delayed addition method

A facile and effective method was successfully developed to prepare the highly cross-linked monodispersed PS particles via soap-free emulsion polymerization, in which the cross-linking agent (DVB) was delayed addition by varying time (Delayed Addition Method, DAM). Through this method, the highly cross-linked monodispersed particles with functional groups on its surface can be prepared. The particles prepared by DAM had a uniform size distribution for the St/DVB and St/HEMA/DVB system. For the St/DVB system, when the cross-linking agent (DVB) was added delay 3 or 7 h, cross-linked PS particles could be successfully prepared without a significant change in the narrow particle size distribution even containing up to 40 wt% of DVB. Similarly, for the St/HEMA/DVB system, by delayed addition of DVB for 3 h, stable and monodispersed polymer particles still could be prepared even the containing of DVB reach to 60 wt%. Moreover, when the feed composition of the DVB kept constant, the longer the delayed addition time of DVB, the better the monodispersity of the cross-linked particles were.

Two-parameter model predictions and θ-point crossover for linear-polymer solutions

We consider the first few virial coefficients of the osmotic pressure, the radius of gyration, the hydrodynamic radius, and the end-to-end distance for a monodisperse polymer solution. We determine the corresponding two-parameter model functions which parametrize the crossover between the good-solvent and the ideal-chain behavior. These results allow us to predict the osmotic pressure and the polymer size in the dilute regime in a large temperature region above the θ point.

Global amine and acid functional group modification of proteins.

A sequential reaction methodology is employed for the complete derivatization of protein thiols, amines, and acids in high purity under denaturing conditions. Following standard thiol alkylation, protein amines are modified via reductive methylation with formaldehyde and pyridine-borane. Protein acids are subsequently amidated under buffered conditions in DMSO using the coupling reagent (7-azabenzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate. The generality of the approach is demonstrated with four proteins and with several amines yielding near-quantitative transformations as characterized by high-resolution Fourier transform mass spectrometry. The developed approach has numerous implications for protein characterization and general protein chemistry. Applications in mass spectrometry (MS) based proteomics of intact proteins (top-down MS) are explored, including the addition of stable isotopes for relative quantitation and protein identification through functional group counting. The methodology can be used for altering the physical and chemical properties of proteins, as demonstrated with amidation to modify protein isoelectric point and through derivatization with quaternary amines. Additionally, the chemistry has applications in the semisynthesis of monodisperse polymers based on protein scaffolds. We prepare proteins modified with azides and alkynes to enable further functionalization via copper(I)-catalyzed 1,3-dipolar Huisgen cycloaddition ("click") chemistry.

A generalized relation between MWD and relaxation time spectrum

An inversion procedure for converting linear viscoelastic properties of polymer melts into molecular weight distribution (MWD) described by the generalized exponential function (GEX) has been implemented and applied in a previous work (Cocchini F, Nobile MR. Rheol Acta 42:232–242, 2003). It is based on the elegant relationship between the relaxation spectrum and the MWD function proposed by Thimm W, Friedrich C, Marth M. J Rheol 43:1663–1672 (1999). In the present paper, such a methodology has been generalized to properly account for sharp MWDs, in particular, nearly monodisperse or blends of nearly monodisperse polymer samples. The generalized relationship has been verified and calibrated using the BSW kernel (Baumgaertel M, Schausberger A, Winter HH. Rheol Acta 29:400–408, 1990) to describe the rheological behavior of some Polystyrene samples from the literature, in terms of the known MWD. Then, it has been successfully applied to the inversion problem for a wider set of samples, with both broad and sharp distributions. The Rouse contribution at high frequencies and the accelerating effect on the relaxation times due to polydispersion have been also addressed.

Functional 3D photonic films from polymer beads

AbstractThis paper describes synthesis and properties of polymer opals with a special emphasis on functional opals. Polymer opals are formed from monodisperse polymer colloids by self‐assembly. Their potential applications range from coloring pigments, 3D bicontinuous supports for catalysis to photonic materials. This latter application requires especially the controlled creation of defects and the incorporation of fluorescent materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reversible Deformation of Opal Elastomers

Synthetic opals result from the crystallization of monodisperse silica or polymer beads of submicroscopic size. The beads self-organize to the face-centered cubic (fcc) lattice from which light is reflected wavelength selectively. At diameters of 0.15−0.3 μm, colors are singled out of white light by diffraction from the 111 plane of the lattice, the reflected color depending on the spacing a111. With elastic opal films of core−shell (CS) beads, this spacing and, thereby, the color can be changed by deformation. This mechanochromic effect has so far been studied only on opals made of beads that were not chemically interconnected so the deformation was partly irreversible. In this study, opal films of polymeric core−shell beads were prepared by a melt-flow technique developed earlier in this institute. Afterward, the films were photo-cross-linked. They deformed indeed reversibly, however, with mechanical hysteresis effects. The strained fcc lattice causes a blue shift of the reflected color, which is indicative of a hard-sphere deformation mechanism. The shift is strong enough to switch monochromatic light on and off by only a few percent strain.

Chemoenzymatic Synthesis with Distinct Pasteurella Heparosan Synthases: MONODISPERSE POLYMERS AND UNNATURAL STRUCTURES

Heparosan (-GlcUA-beta1,4-GlcNAc-alpha1,4-)(n) is a member of the glycosaminoglycan polysaccharide family found in the capsule of certain pathogenic bacteria as well as the precursor for the vertebrate polymers, heparin and heparan sulfate. The two heparosan synthases from the Gram-negative bacteria Pasteurella multocida, PmHS1 and PmHS2, were efficiently expressed and purified using maltose-binding protein fusion constructs. These relatively homologous synthases displayed distinct catalytic characteristics. PmHS1, but not PmHS2, was able to produce large molecular mass (100-800 kDa) monodisperse polymers in synchronized, stoichiometrically controlled reactions in vitro. PmHS2, but not PmHS1, was able to utilize many unnatural UDP-sugar analogs (including substrates with acetamido-containing uronic acids or longer acyl chain hexosamine derivatives) in vitro. Overall these findings reveal potential differences in the active sites of these two Pasteurella enzymes. In the future, these catalysts should allow the creation of a variety of heparosan and heparinoids with utility for medical applications.

The impact of the concept of “Living Polymers” on material science

AbstractThe concept of “Living Polymers” was first introduced in a short communication by M. Szwarc, M. Levy, and R. Milkovich in 1956 and is now widely used in the polymer literature. It led to the synthesis of monodisperse polymers, telechelic polymers, and block copolymers. Living polymerization has evolved in the last 50 years and new methods were developed for various other types of anionic, cationic, ring‐opening, and free radical polymerizations. The field has expanded tremendously and the term “controlled/living” polymerization is commonly used to cover all the methods. A few of the interesting developments in the area are described in this paper. Copyright © 2007 John Wiley & Sons, Ltd.

Synthesis of monodisperse polystyrene microspheres by dispersion polymerization using sodium polyaspartate

We prepared monodisperse polystyrene microspheres by dispersion polymerization using sodium polyaspartate (PAspNa) as a dispersion stabilizer in an ethanol/water medium. The influence of reaction parameters, i.e., the volume fraction of ethanol in the medium, stabilizer concentration, and the monomer concentration, on the average diameter of the prepared polystyrene microspheres and its distribution were investigated. Polystyrene microspheres were successfully prepared, and the average diameter of the prepared monodisperse polystyrene microspheres was controlled by adjusting the reaction parameters. The zeta potential of the microspheres and the time course of conversion, the particle diameter and its distribution, and particle numbers were also examined. It was found that PAspNa as a dispersion stabilizer provides an environmentally benign process for the preparation of monodisperse polymer microspheres by dispersion polymerization.