Ultrahigh Molecular Weight Polymers Research Articles

Elongational viscosity for miscible and immiscible polymer blends. II. Blends with a small amount of UHMW polymer

The effect of miscibility on elongational viscosity of polymer blends was investigated in homogeneous, miscible, and immiscible states by the blend of 1.5 wt % of ultrahigh-molecular-weight (UHMW) polymer. The matrix polymer was either poly(methyl methacrylate) (PMMA), or poly(acrylonitrile-co-styrene) (AS) that has a comparable elongational viscosity value. The homogeneous blend consisted of 98.5 wt % of PMMA and 1.5 wt % of UHMW–PMMA. The miscible blend was composed of AS and UHMW–PMMA at the same ratio. The immiscible blend was a combination of AS and UHMW–polystyrene (PS) at the same ratio. The strain-hardening behavior of the different blends were compared with that of pure PMMA. It was demonstrated that 1.5 wt % of UHMW induces a strong strain-hardening property in the homogeneous and miscible blends but was hardly changed in the immiscible blend. The optical microscope observation of the immiscible blend suggested that the UHMW domains were stretched, but that the degree of domain deformation was less than a given elongational strain. It was concluded that the strain-hardening property is strongly affected by the miscibility of UHMW chain and matrix. The strong strain-hardening property is caused by the deformation of the UHMW polymer. UHMW chains are stretched when they are entangled with surrounding polymers. However, UHMW chains in an immiscible state are not so deformed because of viscosity difference and no entanglements between domain and matrix. A smaller degree of UHMW chain deformation in immiscible state results in weaker strain-hardening property. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 961–969, 1999

FFF-MALS—A New Tool for the Characterisation of Polymers and Particles

As industrial applications for polymers and biopolymers have expanded in recent years, the limitations of traditional characterisation techniques have become apparent. Size exclusion chromatography is widely used to determine the molecular weight distribution of a polymer, but suffers from a number of drawbacks when used with ultra-high molecular weight (MW) polymers or polyelectrolytes. As a result, interest in the use of field flow fractionation (FFF) for the separation of macromolecules has grown. FFF relies on a combination of field-driven and diffusive transport mechanisms to separate polymers in the range 103–1015gmol-1 and/or particles of 5nm–100μm, allowing MW and size distributions for virtually all macromolecules to be determined without the need for filtration. The open channel geometry minimises shear effects making it possible to separate fragile, high MW polymers, while the absence of a stationary phase means adsorption effects can be minimised. As a result, samples can be run in a mobile phase suitable for the polymer rather than selecting conditions to minimise column interactions which leads to the risk of aggregate formation in polyelectrolytes. While it is possible to calculate the MW of a polymer eluting from an FFF channel using calibration techniques similar to those for size exclusion chromatography, the same problems are encountered as well. When analysing ultra-high MW polymers and/or gels, these are compounded by the need for calibration standards with a MW in excess of 106gmol-1. The addition of multi-angle light scattering (MALS) to FFF has allowed absolute MW and size distributions to be obtained without the need for calibration, standards or assumptions. Complex mixtures of polymer, microgel, and macrogel can all be studied in a single run. By combining all of the information derived from FFF–MALS, molecular conformation, density and branching levels can also be determined. This paper outlines the principles of operation of FFF–MALS, before moving on to discuss recent applications of the technique for the analysis of macromolecules and sub-micrometre particles. © 1997 SCI

High molecular weight poly(4-trimethylsilyl-1-buten-3-yne)

Selective polymerization of 4-trimethyl-1-buten-3-yne through the vinyl group, followed by cleavage of the protective trimethylsilyl group, was attempted as a possible route for obtaining high molecular weight poly(vinylacetylene). Anionic polymerization and thermally initiated radical polymerization did not lead to a high molecular weight polymer. This was explained by the possibility of acetylene-allene rearrangements leading to transfer reactions. At low temperatures, in the absence of transfer reactions, the monomer was found to be capable of a self-initiated polymerization leading to an ultra-high molecular weight polymer.

Application of thermal field-flow fractionation for characterization of industrial polymers

Applicability of ThFFF for the analysis of industrial polymers is briefly discussed. For homopolymers, ThFFF separates molecules based on the molecular weight (MW), and thus provides molecular weight distribution (MWD) of the sample. As the ThFFF channel is empty, sample filtration is not required and non-ideal SEC phenomena such as adsorption or shear degradation of polymers are minimized in ThFFF. Thus ThFFF is expected to be more useful than SEC for the determination of MW and MWD of ultrahigh MW polymers. For polymers having MW lower than about 10,000, SEC provides better resolution, and is more useful than ThFFF. ThFFF calibration procedure and some important experimental ThFFF parameters are also discussed. ThFFF can provide a composition-based separation as well as the size-based separation. This unique capability of the ThFFF provides new possibilities for the characterization of various industrial copolymers and blends. The capability of ThFFF for the analysis of microgel-containing polymers is described including the determination of gel content. In SEC, microgel particles are excluded from the pores of the packing material and thus co-elute. By contrast, a size-based separation of gel particles may be obtained in ThFFF. © 1997 John Wiley & Sons, Inc. J Micro Sep9: 281–286, 1997

The effect of ultrahigh molecular weight polymers on the nonlinear response in uniaxial elongational viscosity

The effect of ultrahigh molecular weight polymers on the nonlinear response in uniaxial elongational viscosity

Separation of Polysaccharides by Thermal Field-Flow Fractionation

Abstract Polysaccharides are complex polymers of great biological and industrial importance. The fractionation and determination of molecular weight distributions of these substances are required for many applications. Thermal field-flow fractionation (thermal FFF) is shown to be applicable to the separation and characterization of a variety of polysaccharides in dimethyl sulfoxide (DMSO). Samples of pullulans, dextrans, and Ficolls are readily fractionated according to differences in molecular weight. Calibration plots have been developed to obtain molecular weight distributions. More complex polysaccharides, such as starch and cellulose, have also been investigated. This study is complicated by the poor solubility of these materials. Nonetheless, starch can be successfully separated into amylose and amylopectin fractions, the latter consisting of an ultrahigh molecular weight polymer with a highly branched structure. A cationic corn starch has also been resolved into its components. These examples sugge...

Influence of operational parameters on retention of ultra-high molecular weight polystyrenes in thermal field-flow fractionation

The influence of various parameters (concentration of the injected polymer solution, flow rate, temperature gradient, relaxation conditions) on the retention and shape of the fractogram of ultra-high molecular weight polystyrenes in thermal field-flow fractionation was investigated. Under the operating conditions adopted, reproducible oscillations in the peak shape are observed for molecular weights larger than a few millions, especially at relatively high polymer concentration. They are attributed to some hydrodynamic instabilities. The retention of ultra-high molecular weight polystyrenes at high flow rate is strongly dependent on the initial relaxation period. All of the investigated operational variables have a complex effect on the resulting shape of the fractogram. Consequently, the confirmation of the shear-induced focusing of macromolecules across the channel thickness requires further study. Experiments on reinjection of fractions collected after an initial high speed pass through the separation system leads to the conclusion that shear degradation of the ultra-high molecular weight polymers did not occur under the investigated experimental conditions even at the highest flow rates.

The initiation activity and kinetic behaviour of the volatile products of plasmas in methyl methacrylate polymerization

It was found that the volatile products of plasmas of methyl methacrylate, vinyl acetate and methyl isobutyrate can actively initiate the polymerization of methyl methacrylate to produce ultra high molecular weight polymers. The block copolymer can be obtained by programmed feeding of the monomers. The volatile products of the plasmas are living free radicals with a very long lifetime as shown by e.s.r. studies. The reaction kinetics were determined by monitoring the conversion of polymerization with a dilatometer. It is concluded that the polymerization of methyl methacrylate initiated by the volatile products of the plasmas occurs by a quasi-living free radical mechanism with instantaneous initiation and monomer transfer. The results of the conversion curve and the molecular weights calculated by non-steady-state kinetics according to this mechanism are consistent with the experimental results.

Interpretation of long-chain structure from dilute solution properties of ultrahigh molecular weight polymers

Systematic studies on solution properties of ultrahigh molecular weight polymers showed the existence of some special features as compared to usual length polymers. The paper discusses the possible appearance of branched structures in the polymerization process, structures able to influence the mentioned features. From experimental data on poly(methyl methacrylate), poly(butyl methacrylate) and polyacrylonitrile it appears that branching can be excluded, and the very high molecular weight domain considered may be responsible for the modifications observed in the molecular weight dependences on , A2 or [ν].

Solution properties of ultrahigh molecular weight polymers. 17. Conformational transitions of poly(isobutyl methacrylate) in dilute solution

AbstractThe temperature dependence of viscosity of ultrahigh molecular weight poly(isobutyl methacrylate) fractions in dilute solution has been investigated. A discontinuity of intrinsic viscosity was observed in the temperature range 20 to 30°C. The study of unperturbed dimensions and polymer‐solvent interaction parameters shows that both inter‐ and intramolecular interactions are affected. This effect modifies the flexibility of the macromolecular chain and other properties in solution.

Technical Notes: Rotary Meter for Sequential Injection of Corrosive Fluids

A custom meter capable of handling corrosive fluids was developed to control sequential injection as part of an experimental probe-type fertilizer injector. The meter transmitted pressurized fluid from a stationary housing to a rotor and crankshaft assembly that revolved within the housing. Size and location of a slot in the flat rotor face dictated duration and timing of the injection interval. To maintain sealing and to compensate for wear between component contact surfaces, a unique floating pressure plate assembly faced with ultra high molecular weight (UHMW) polymer was located between the housing and rotor. Triple o-ring rotary seals installed using modified manufacturer-recommended groove dimensions prevented leaking of fluid from the meter. The meter operated successfully in laboratory and field evaluations of the fertilizer injector.

Radiation-induced crystallinity changes in linear polyethylene: Long-term aging effects in pressure-crystallized ultra-high molecular weight polymer

Abstract It has been shown previously that linear polyethylenes undergo increases in crystallinity and peak melting temperature after irradiation, the magnitude of the effects being dependent upon the dose and the molecular weight of the polymer. The crystallinity was also found to increase with time after irradiation (aging) up to 112 months, although peak melting temperature declined slowly with aging time. The results were explained in terms of the scission of tie molecules followed by the slow growth of new crystal lamellae. This paper presents similar studies on a single ultra-high molecular weight polyethylene resin which has been crystallized under 5.1 kbar pressure. As before, irradiation causes an immediate rise in crystallinity followed, over a period of 93 months, by further increases. The highest crystallinity achieved by this combination of pressure crystallization, irradiation, and aging is some 82%. This demonstrates that UHMWPE is intrinsically capable of the same degree of crystallinity a...

High speed separation of ultra‐high‐molecular‐weight polymers by thermal/hyperlayer field‐flow fractionation

A process for high speed separation of ultra-high molecular weight polymers using a hyperlayer field-flow fractionation technique comprising forcing a carrier fluid containing a small sample of the high molecular weight polymer through a thin flow channel possessing an accumulation wall, applying a primary externally controlled driving force transversely across the thin dimension of the channel, adjusting the flowrate of the fluid and the field strength of the primary externally controlled force in relationship to the channel thickness such that at least over part of the molecular weight range the entropic force F e and the primary driving force F 1 are related by the inequality |F e |>|F 1 | at the accumulation wall of the channel.

Solution properties of ultrahigh molecular weight polymers, 15. A viscometric study of poly(isobutyl methacrylate) in different solvents

AbstractThe paper extends previous studies on ultrahigh molecular weight synthetic polymers. The intrinsic viscosities and the viscosity constants of poly(isobutyl methacrylate) fractions were obtained by the methods of Huggins, Kraemer, Martin, Schulz‐Blaschke, and Fedors in CCl4 and C6H6 at 25°C. It was observed that the method of Fedors is not very sensitive to the possible errors appearing in estimating the relative viscosities in higher concentration domains. This method yields intrinsic viscosity values close to the mean values obtained from the other five methods and to the values calculated according to the averaging procedure suggested by Sakai. The transition concentrations separating the concentration domains (diluted‐semidiluted) and the Mark‐Houwink constants were obtained.

Solution properties of ultrahigh molecular weight polymers. VII. Conformational characteristics of poly(butyl methacrylate)

AbstractThe paper is concerned with light scattering studies on solutions of ultrahigh molecular weight poly(butyl methacrylate). The dependence of the radius of gyration and of the second virial coefficient on the weight‐average molecular weight of the polymers was established in methyl ethyl ketone, dimethylformamide, and CCl4. Short‐range and long‐range interactions were discussed in terms of the steric factor σ, of the interaction parameter B, and of the interpenetration function ψ(z).

Solution properties of ultrahigh molecular weight polymers: 11. A viscometric study on the excluded volume effect of poly(butyl methacrylate)

The intrinsic viscosities and the viscosity constants of ultrahigh molecular weight poly(butyl methacrylate) fractions were obtained by the Huggins, the Kraemer, the Martin, the Schulz-Blaschke and the Fedors methods in methyl ethyl ketone. It was concluded that the averaging procedures suggested by Sakai for intrinsic viscosities are close to the values resulting from Fedors' method. The Mark-Houwink constants were obtained. The interpenetration functions Ψ( z) and Π( z) were discussed on the basis of different theoretical approaches through the expansion factors α s( z); the renormalized group theory of Douglas and Freed was found to confirm best with the expeirmental results.

Solution properties of ultra-high molecular weight polymers—13. Viscosity-molecular weight relationships and unperturbed dimensions of poly(butyl methacrylate) in various solvents

The behaviour of ultra-high molecular weight poly(butyl methacrylate) ( M w = 9.59 × 10 6–24.50 × 10 6 ) in dilute solution in methyl ethyl ketone, benzene, dioxane, and cyclohexanone, at 25°C, has been investigated by viscometry. Mark-Houwink relations have been established, and the unperturbed dimensions have been determined and compared with those previously obtained in a θ-solvent.

Solution properties of ultrahigh molecular weight polymers. 12. Systematic error sources affecting the discussion of the excluded volume effect

AbstractThe paper is concerned with the error sources appearing in viscometric and light scattering determinations in solutions of ultrahigh molecular weight polymers and with the influence of these errors in discussing the excluded volume effect for very high excluded volume parameters.

Solution properties of ultrahigh molecular weight polymers. 5. Conformational changes of butyl methacrylate-styrene copolymers in dilute solution

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolution properties of ultrahigh molecular weight polymers. 5. Conformational changes of butyl methacrylate-styrene copolymers in dilute solutionCristofor I. Simionescu, Bogdan C. Simionescu, and Silvia IoanCite this: Macromolecules 1985, 18, 10, 1995–1999Publication Date (Print):October 1, 1985Publication History Published online1 May 2002Published inissue 1 October 1985https://doi.org/10.1021/ma00152a033RIGHTS & PERMISSIONSArticle Views52Altmetric-Citations6LEARN 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 PDF (539 KB) Get e-Alerts Get e-Alerts

Cryogenic degradation of polystyrene in solution

An ultra-high molecular weight and narrow distribution polystyrene ( M w = 7.3 × 10 6 , M w/M n = 1.13) was dissolved in a wide range of solvents. Potential degradation by freezing was studied as a function of solvent type, concentration, cooling rate and number of freezing cycles. Cryogenic experiments were conducted in dioxane, tetrahydrofuran, benzene, dichloroethane, cyclohexanone, p-xylene, methyl methacrylate and styrene. The extent of degradation did not relate to a single solvent parameter, but there seemed to be a tendency towards a limited degradation in solvents with low melting points and/or solubility parameters greatly different from that of polystyrene. A low polymer concentration as well as a high cooling rate promoted chain scission, the latter parameter being the most important. In cyclohexanone and p-xylene, linear relationships were observed between the number of scission per molecule and the number of freezing cycles at high polymer concentrations and at high cooling rates. At lower concentrations and slower cooling, the relationships were non-linear suggesting a different degradation mechanism. The most extensive change in molecular weight distribution was observed on freezing in styrene. After 45 freezing cycles, an M w of only 2.3 × 10 6 was observed. The results indicate that chain scission occurred together with polymerization and combination reactions. Freezing of suitable solutions of ultra-high molecular weight polymers can thus be used as a new way of initiating polymerizations by cooling rather than heating.