Monodisperse Polymer Research Articles

Aggregation and Critical Micelle Concentrations of Polystyrene-b-poly(sodium acrylate) and Polystyrene-b-poly(acrylic acid) Micelles in Organic Media

Block copolymer micelles formed from polystyrene-b-poly(sodium acrylate) (PS-b-PANa) and polystyrene-b-poly(acrylic acid) (PS-b-PAA) were characterized in organic solvents. The critical micelle concentrations (cmc's) were determined for one block copolymer series in which PS blocks of 660 units were attached to either relatively short PANa or PAA blocks ranging in length from 2.6 to 18 units. The cmc's for these block copolymers in toluene, tetrahydrofuran (THF), and chloroform were found to range from ca. 1 × 10-7 to 5 × 10-9 M. The a and b constants in the relation log Ci = aNi1/3 + b, where Ci is the cmc for a monodisperse polymer and Ni is the insoluble block length were evaluated and correlated to the polymer−solvent interaction parameters for the present systems as well as for several other block copolymer micelles. The PS(660)-b-PANa(x) series was also investigated by size exclusion chromatography (SEC) in THF. Two peaks in the SEC chromatograms could be distinguished, one corresponding to micellized block copolymers and the other to unassociated chains. The position of the latter peak was the same as that of the PS homopolymer, which was also present. These micelles were also characterized by static and dynamic light scattering (SLS and DLS). The effect of the soluble (PS) block length on the aggregation was investigated by SLS in THF. For this study, three additional PS-b-PANa series containing PS block lengths of 190, 630, and 2300 units attached to PANa blocks ranging in lengths from 4.2 to 69 units were characterized. The aggregation numbers (Nagg) were found to be influenced significantly by the soluble PS block length (NPS). The Nagg and the calculated core radii (Rc) were found to scale with the block lengths as Nagg ∝ NPANa0.5NPS-0.6 and Rc ∝ NPANa0.5NPS-0.2.

Biochemical and biomedical application of monodisperse polymer particles

AbstractMacroporous particles with large pores are used for size exclusion chromatography of carbohydrates with very high molecular weights. Macroporous particles of different sizes are used for multiple immunofluorometric analysis by flow cytometry. Porous magnetic particles with protein A coupled to the surface of the pores combine a high capacity in binding of IgG with easy handling of the particles. Magnetic beads with boronic acid coupled to the surface are applied for selective isolation of subclasses of cells. The beads are detached from the cells by addition of sorbitol, leaving free, pure cell fractions in good yield. The use of magnetic particles in molecular biology is described.

Preparation of colored poly(styrene‐co‐butyl methacrylate) micrometer size beads with narrow size distribution by dispersion polymerization in presence of dyes

AbstractThe preparation of monodisperse polymer particles formed by a dispersion copolymerization of a system containing styrene, butyl methacrylate, and nonpolymerizable dyes has been studied. Both the polarity of the ethanol–water dispersion medium and the polymerization rate were found to have a significant effect on the particle size. Experimental conditions have been determined that enable the preparation of colored beads having a narrow size distribution. While the benzoyl peroxide initiated polymerization is seriously inhibited by the presence of dyes, polymerization with azobisisobutyronitrile in presence of the black dye Nigrosin affords monodisperse beads in a high yield. © 1995 John Wiley & Sons, Inc.

Monodisperse polymer beads as packing material for high‐performance liquid chromatography. Preparation of macroporous poly(2,3‐epoxypropyl vinylbenzyl ether‐co‐divinylbenzene) beads, their properties, and application to HPLC separations

AbstractIn search for HPLC separation media with new surface chemistries, a styrene‐based monomer, 2,3‐epoxypropyl vinylbenzyl ether, containing reactive epoxide groups has been syn‐thesized and copolymerized with divinylbenzene in a suspension polymerization. The process involves the use of size monodisperse particles that are swollen with monomer and then polymerized in the presence of a porogenic diluent consisting of a mixture of 4‐methyl‐2‐pentanol and octane. The effect of concentration of divinylbenzene on the pore size dis‐tribution and the specific surface area of the resulting uniformly sized porous poly(2,3‐epoxypropyl vinylbenzyl ether‐co‐divinylbenzene) beads has been studied. The epoxide groups of the copolymer have been hydrolyzed and the beads used for reversed‐phase chro‐matography of both small molecules and proteins to show the effect of hydrophobicity of the matrix on the separation properties. Reversed‐phase chromatography of alkylbenzenes follows the expected pattern while for proteins the hydrolyzed beads with the highest content of the crosslinking monomer exhibit a remarkable deviation from the predicted retention characteristics. © 1995 John Wiley & Sons, Inc.

Preparation of hydrophilic monodisperse microspheres by radiation precipitation polymerization and its characteristics

A new preparation method for monodisperse polymer microspheres with a hydrophilic property has been investigated by utilizing an irradiation method. Hydrophilic microspheres were synthesized by radiation precipitation copolymerization using polyethylenglycol dimethacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, and methacrylic acid monomer. The diameter of the microspheres prepared was 0.3–1 μm, in which the irradiation was carried out without catalyzer at room temperature for 1 hr at a dose rate of 10 kGy/hr with γ-rays from a Co-60 source. The diameter of the microspheres increased with increasing hydrophilicity of monomer.

Determination of Flory–Huggins interaction parameter and self-diffusion coefficients in ternary polymer solutions by quasielastic light scattering

We present a new method to determine the Flory–Huggins polymer–polymer interaction parameter and self- (or tracer) diffusion coefficients in a ternary polymer solution made of two monodisperse polymers and a solvent by quasielastic light scattering (QELS). Previously proposed methods based on the random phase approximation (RPA) were restricted to special cases with two polymers having the same molecular weight and identical interaction parameters with the solvent. The present method (also using RPA) has removed these restrictions. It is applicable to an arbitrary ternary solution with polymers having different molecular weight and solvent interaction parameters. To illustrate, we have analyzed the published QELS data of the PDMS/PMMA/toluene ternary system to obtain self diffusion coefficients for each polymer and the Flory–Huggins polymer–polymer interaction parameter as a function of polymer composition in the system.

Synthesis of functional polymers bearing pendant mono‐and oligo‐saccharide residues

AbstractThe present paper focuses on (i) a new synthetic methodology to prepare vinyl ether‐based synthetic glycoconjugates (glycopolymers) with well‐controlled structure, and on (ii) the application of glycopolymers bearing modified disaccharide residue as thermotropic liquid crystalline (LC) materials. Two vinyl ethers (VEs) having pendant glucose residues with their hydroxyl functions protected by acetyl and isopropylidene groups, respectively, were found to undergo living cationic polymerization initiated by a HI/ZnI2‐initiating system. Deprotection of the resultant monodisperse polymers led to water‐soluble polymers bearing a pendant glucose residue. Sequential living block copolymerization of glucose‐containing VE and alkyl VE, and subsequent deprotection afforded an amphiphilic block copolymer of well‐controlled structure. Transmission electron microscopic observation of its cast thin film revealed microphase‐separated surface morphologies that varied with varying segment composition ratio. A VE substituted with a heptadecanoated cellobiose pendant was independently prepared, and was cationically polymerized to give a thermotropic LC polymer. From X‐ray analysis, the mesophase was assigned to a discotic columnar in type, in which each main chain, extended due to the steric repulsion between the neighboring bulky pendants, was surrounded by three discotic columns.

Rheology and diffusion of concentrated monodisperse and bidisperse polymer latices

Three monodisperse, electrostatically stabilized latices of different sizes (306, 164 and 64 nm) have been synthesized by emulsion polymerization of styrene and acrylic acid, and purified by ion-exchange. Particle size and size distribution were determined by transmission electron microscopy as well as static and dynamic light scattering from dilute dispersions in various aqueous media. Electrostatic properties were determined through titration and ξ-potential measurements. Concentrated colloidal suspensions at different volume fractions up to 50%, and various pH and ionic strengths have been studied with regard to their microscopic dynamics by fiber-optic quasielastic light scattering (FOQELS). At high ionic strength, the concentration dependence of the diffusion coefficient was in agreement with theoretical predictions for the self-diffusion of hard spheres. At low ionic strength, significant deviation from hard-sphere behavior was observed and FOQELS provided an optical technique for determining the presence of a yield stress. The same samples have been studied in various rheometrical tests. At low ionic strength elastic properties dominated; at high ionic strength, samples were predominantly viscous. Intermediate viscoelasticity, at well balanced strength of interaction, could be detected. The transition from viscous to elastic character occurred over a narrow regime of ionic strength or concentration. Curves of storage modulus, G′ versus frequency, ω, at different particle contents in the viscoelastic region could be shifted to a mastercurve by scaling ω with the longest relaxation time. Bimodal mixtures of small and large particles were also investigated by means of viscometry and FOQELS. When the number concentration of large spheres was small, FOQELS could be used to measure a probe-diffusion that showed a concentration dependence similar to that of viscosity and which resembled the behavior of long-time self-diffusion.

Morphologies of micron‐sized monodispersed composite polymer particles having crosslinked structures produced by seeded polymerizations

AbstractThree kinds of micron‐sized monodispersed polystyrene (PS)/ poly(styrene ‐ divinylbenzene) composite particles were produced by two kinds of seeded copolymerizations of styrene (S) and divinylbenzene (DVB) (PS seed/ (S+DVB)=2/1, wt. ratio; S/DVB=1/1, molar ratio) in the presence of about 2 μm‐sized monodispersed PS particles, and their morphologies were examined. One was produced by a seeded dispersion copolymerization where almost monomers and initiators exist in an ethanol/water (12.6/4.0, w/w) medium. The others two were produced by seeded copolymerizations with the dynamic swelling method where almost monomers exist in the monomer‐swollen particles using 2, 2'‐azobisisobutyronitrile in monomer‐swollen PS seed particles or using 4, 4'‐azobis (4‐cyanopentanoic acid) in an ethanol/water (7/43, w/w) medium. In the former polymerization, the produced composite particles had a high dense crosslinked shell, whereas in the latter two polymerizations, they did the comparatively homogeneous crosslinked structures.

α-Particle Radiotherapy with 211At-Labeled Monodisperse Polymer Particles, 211At-Labeled IgG Proteins, and Free 211At in a Murine Intraperitoneal Tumor Model

Four different chemical forms of the α-particle emitting radionuclide 211 At were injected intraperitoneally in mice inoculated intraperitoneally 30 hr in advance with 106 cells of the K13 murine hybridoma cell line. The different 211At forms were (a) free 211At, (b) 211At-labeled TP-3 nonspecific monoclonal antibody (211At-TP-3), (c) 211At-labeled human IgGκ (211At-hIgGκ), and (d) 211At-labeled monodisperse polymer particles (211At-MDPP). A significantly prolonged survival (P < 0.05) was observed with injected doses down to 7 kBq for the 211 At-MDPP, and down to 25 kBq for 211At-hIgGκ. There were no significant differences in survival between 211 At-MDPP, 211At-hIgGκ, and 211At-TP-3 at the dose level of 200 kBq. The group receiving 250 kBq free 211At per animal had a shorter survival than the three other forms at 200 kBq. The groups treated with 500, 200, and 65 kBq 211At-MDPP had a similar survival. The group given the highest dose of 211At-hIgGκ (275 kBq) had the highest fraction (50%) of long-term survivors of all groups. Biodistribution measurements and total body scintigrams in mice without tumor revealed that the free 211At was distributed all over the body within 10 min after injection while at 2 hr a high fraction of the 211 At-TP-3 and 211At-hIgGκ was still present intraperitoneally. In conclusion this study indicates that 211 At-labeled MDPP and 211At-labeled IgG's may be efficient tools for treatment of intraperitoneal superficial tumor cells and malignant ascites.

Stretch transition in a polymer brush.

The behavior of a grafted chain of length K inside an otherwise monodispersed (of length N) polymer brush is investigated. For the case of K\ensuremath{\le}N, the stretching of the chain increases abruptly as K approaches N, analogous to the coil-stretch transition. By generalizing previous results, we derive the scaling forms for the stretching parameter and its mean square fluctuations. We also extend our investigation to the K&gt;N regime and obtain results for the stretching parameter by scaling calculations. We show that the chain is maximally stretched as K\ensuremath{\rightarrow}N from above. Furthermore, we perform a Monte Carlo simulation using the bond-fluctuation model to study the chain end position and its fluctuations. Our data indicate that both the stretching of the chain and its fluctuation are maximal at K=N and the system exhibits a first-order phase transition. The scaling form for the stretching parameter is verified and the scaling function is obtained.

Continuous thermodynamics for polydisperse polymer solutions

Continuous thermodynamics is a framework which combines continuum modeling for the compositions of complex and multicomponent mixtures with molecular thermodynamic models and efficient numerical methods. In this work, a generalized molecular-thermodynamic model for polydisperse polymer solutions is developed; it is formally similar to the classical Flory-Huggins theory but with a polymer-size dependent and polymer-concentration dependent Flory parameter. Most existing lattice models and equation-of-state models such as the Guggenheim, Orifino-Flory, Koningsveld-Kleintjens, Sanchez-Lacombe and Revised Freed models can be cast into this generalized model but with different polymer-size and polymer-concentration dependence for the Flory parameter. A generalized continuous-thermodynamics framework based on this generalized model is also presented; expressions for chemical potentials, spinodals and critical points are derived using both the discrete multicomponent method and the continuous functional procedure. Internally consistent results are obtained. Criteria for multiple critical points are also derived. Computer programs are established for polydisperse-polymer solutions with either a standard or an arbitrary distribution for the polymer's molecular weight; in the latter case, the derivative method is applied, based on a previously developed spline fit. To illustrate the framework developed here, calculated liquid-liquid-equilibrium phase diagrams are shown, including UCST, LCST and hour-glass-shaped cloud-point curves, shadow curves, spinodals, critical points and their dependence on molecular parameters, on pressure and on molecular-weight distribution properties. used in those equations derived from Δ mix G. A binary energy parameter and a binary size parameter are used to fit experimental critical coordinates. Cloud-point curves, shadow curves, spinodals and critical points have been calculated under various conditions which cover different types of liquid-liquid-equilibrium phase equilibria including UCST, LCST and hour-glass shaped phase diagrams. If we have experimental critical points, spinodals, cloud-point curves and shadow curves, we can obtain the binary energy parameter and the binary size parameter as well as their temperature dependence if the experimental data cover a significant temperature range. Considering the difficulty of obtaining monodisperse polymer samples, we can now use a polydisperse polymer sample with a known molecular-weight distribution for experimental work (e.g. cloud points) and then use the parameters obtained experimentally to calculate phase-equilibrium properties for the same system but with a different molecular-weight distribution. Two different procedures, i.e., the discrete multicomponent method and the continuous functional method, have been used for deriving equations. Consistent results have been obtained by both methods. The discrete method is rigorous because polymer components are discrete. A continuous distribution function is only used to calculate various moments in those expressions. The functional method has the merit of mathematical integrity such that the continuous distribution function is built inside the whole framework. While the composition is, in fact, discrete, the continuous distribution provides a good approximation. The present work is only for solutions containing one solvent and one polydisperse polymer. Work in progress extends the methods discussed here to systems containing mixed solvents or mixed polymers and polymer blends with polydisperse polymers.

Internalization of Vibrio salmonicida in isolatedmacrophages from Atlantic salmon ( Salmo salar) and rainbow trout ( Oncorhynchus mykiss) evaluated by a paired immunofluorescence technique

A procedure was developed to culture isolated head kidney macrophages fromsalmonid fish and to study their phagocytic activity. The method was used to compare in vitro macrophage phagocytic activity against Vibrio salmonicida in rainbow trout and Atlantic salmon. These two species of salmonid fish differ in their natural resistance to V. salmonicida, with rainbow trout being more resistant. In both species, the isolated cell population from head kidney had morphological and functional characteristics typical of macrophages. The cells' functional activities were evaluated by studying their ability to grow and adhere to glass, to phagocytise uncoated monodispersed polymer beads, their acid phosphatase activity, and their uptake and degradation of bacteria in a phagocytic assay. To distinguish between extra cellular/cell-adherent bacteria and intracellular bacteria, a paired immunofluorescence technique was developed, based on monoclonal antibodies identifying epitopes on the lipopolysaccharide component of the bacterium. A unique identification of bacterial localisation was achieved by sequential incubation steps with intermittent cell membrane permeabilisation with absolute ethanol. At initial time points macrophages from rainbow trout exhibited a significantly higher phagocytosis of unopsonised V. salmonicida, compared to Atlantic salmon macrophages. Phagocytosed bacteria were easily degraded intracellularly, but fragments of the bacterium were identified by the two monoclonal antibodies at 72 h after inoculation.

An improved algorithm for calculating relaxation time spectra from material functions of polymers with monodisperse and bimodal molar mass distributions

Using the basic concept of Emri and Tschoegl, the algorithm for calculating relaxation time spectra has been improved such that excellent results are provided in the difficult case of polymers with narrow molar mass distributions. These spectra can be compared with those calculated by nonlinear regularization (Weese 1992), which we regard as a very exact method, and show equally good results with even less mathematical effort. Examples of dense relaxation time spectra (up to eight points per decade) are given for nearly monodisperse polystyrene melts and for mixtures of these up to four components. The relaxation time spectra describe the dynamic mechanical experimental data in each case with an overall error of less than 3%. The filtering method used to avoid physically senseless oscillations has been proven to resolve the characteristic peaks contributed by monodisperse polymers accurately.

Molecular weight distribution of poly(dimethylsiloxane) by combining matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry with gel‐permeation chromatography fractionation

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) allows detection of large molecules such as those present in synthetic and natural macromolecules. Until recently, it was reported that MALDI‐TOF measurements can provide correct molecular weight (MW) estimates only for nearly monodisperse polymer samples. We have now developed a methodology for polydisperse samples. We recorded the gel‐permeation chromatography (GPC) trace of a polydisperse polymeric sample of poly(dimethylsiloxane) (PDMS), collecting 42 fractions. Selected fractions were analyzed by MALDI‐TOF and the average MW of each fraction was determined, allowing a calibration of GPC curves against absolute MW. The calibrated GPC trace was then used to compute average MW and molecular‐weight distribution (MWD) of the unfractionated poly(dimethylsiloxane) sample. In the spectra of low molecular‐weight fractions, the resolution is high enough to resolve the contributions of the various PDMS oligomers as separate signals.

Structure and swelling of end-linked model networks

In the framework of the three-dimensional bond-fluctuation model, the formation and swelling of end-linked monodisperse polymer networks is simulated. The kinetics of cross-linking show a cross-over from reaction controlled to diffusion-limited behaviour, depending on the reaction rate.On small scales the internal dimension of the resulting networks is ca. 1.3 while on large scales it adopts the dimension of 3. The cross-over between both regions can be interpreted as a back-folding mechanism leading to internal dimensions larger than 3 at intermediate scales. The same behaviour was previously obtained by simulating randomly cross-linked networks.In marked contrast to some theoretical models, the networks deform in a highly non-affine manner upon swelling. Small substructures swell much less than the whole sample as determined from the occupation density at the centre of the simulation lattice. More precisely, the swelling degree is a monotonically increasing function of the scale under consideration. This can be related to the unfolding of the network structure at scales much larger than a single precursor chain.

Two-Dimensional High-Performance Liquid Chromatography Using Monodisperse Polymer Beads Containing Segregated Chemistries Prepared by Pore Size Specific Functionalization. Single-Column Combinations of Size Exclusion or Ion Exchange with Reversed-Phase Chromatography

Separation media for the complete separation of complex samples that require a combination of size exclusion or ion-exchange with reversed-phase chromatographic modes in a single column have been prepared from size monodisperse 10 microns poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads using a pore size specific functionalization process. To achieve the first combination of chromatographic modes, the large pores of the beads were selectively hydrolyzed to diols using aqueous poly(styrenesulfonic acid), while highly hydrophobic octadecyl groups were introduced into the small pores by reaction of the remaining epoxide groups with octadecylamine. These beads provide excellent protein recoveries and may be used for the direct injection separation of samples containing both hydrophilic proteins and hydrophobic drugs. Beads containing diethylamino groups in the large pores and octadecyl functionalities in the small pores were also prepared by size-selective modification. A plot of log k' against ionic strength of the mobile phase for these beads shows the absence of hydrophobic interactions and documents the clean ion-exchange mechanism of protein separation. Examination of the small pores in both types of separation media confirmed that their hydrophobicity was sufficient to allow the separations of small molecules in reversed-phase mode. Column packed with these dual-chemistry beads exhibited high efficiencies and were used successfully for the separations of proteins and alkylbenzenes or drugs.

A new technique for preparing monodisperse polymer particles. II. Phase separation mechanisms

AbstractNylon 6 polymer particles with a narrow‐size distribution are made by phase separation of different concentrations of polymer solutions. At concentrations above 0.15 wt %, the diameter of the precipitated particles increases linearly with the increasing of polymer concentration. The experimental results suggest that coagulation plays an important role in particle growth during the propagation stage. A mechanism is proposed for the formation of monodisperse polymer particles during phase separation. The uniformity of the precipitated nylon 6 particles decreases when the cooling process is slowered. The surface morphologies of the nylon 6 particles are controlled by changing the drying conditions. © 1994 John Wiley &amp; Sons, Inc.

The recovery of polymer melts after shear and elongational flows

This work examines the constrained recoil after steady shear flow and the free recovery after steady elongational flow of monodisperse polymer melts. Calculations are performed in the framework of the Curtiss–Bird theory using both conventional numerical integrations and nonequilibrium Brownian dynamics. The latter approach is shown to have significant advantages, particularly at high shear or elongational rates. The predicted curves of recovery as a function of shear rate exhibit an unusual maximum for which several explanations are proposed.

Instabilities of a stagnation point flow of a dilute polymer solution

The time-dependent planar flow of a dilute monodisperse polymer solution is considered in the limit where inertia is negligible. The polymers are modelled as linear-locked dumbbells with non-linear hydrodynamic friction, and the flow field is chosen to contain an isolated stagnation point. For Weissenberg numbers We above a critical value, here taken to be unity, the steady flow in this geometry contains a highly viscous birefringent strand along the outgoing flow axis, of approximately uniform width, within which the polymers are fully extended. It is shown that for sufficiently high polymer concentrations this steady flow is subject to two modes of instability: for modest Weissenberg numbers ( 1 < We < 2) an oscillatory varicose disturbance of the strand is linearly unstable; for higher Weissenberg numbers a strand-disturbance having a sinuous component gives rise to a finite amplitude instability. The amplitude of initial disturbance required to trigger this instability is shown to be small. The parameter regimes for concentration, Weissenberg number and polymer extensibility within which each instability occurs are found to be in qualitative agreement with the opposed jets experiments of A.J. Müller, J.A. Odell and J.P. Tatham, J. Non-Newtonian Fluid Mech., 35(1990)231–250. The mechanism of the instability is kinematic in character: flow perturbations modify the polymer stretch and after a time delay, given by the time taken for polymers entering the flow to become fully stretched, the birefringent strand is affected. This in turn modifies the flow further, and if the polymer concentration is high enough gives an oscillation of increasing amplitude.