Broad Molecular Weight Distribution Polymer Research Articles

Stable Free-Radical Emulsion Polymerization

Polymerizations of styrene under emulsion stable free-radical polymerization conditions are reported. Precipitation of an acetone solution of a low molecular weight TEMPO-terminated polystyrene into an aqueous solution of poly(vinyl alcohol) enables the formation of emulsion particles that can be swollen with monomer and subsequently polymerized. The polymerizations proceed in a living manner, yielding polymers that show an incremental increase in molecular weight with time and have narrow molecular weight distributions. Plots of number-average molecular weight versus conversion are linear, indicating a controlled polymerization. The resulting latexes are colloidally stable, and particle size distributions are Gaussian with an average particle diameter of 450 nm. These results constitute the first successful example of an SFRP emulsion process in which the product is not contaminated with a conventionally produced broad molecular weight distribution polymer.

Using a differential refractive index detector as a pressure transducer for online viscometry in exclusion chromatography

A differential refractive index (DRI) detector was tested as a pressure transducer for single capillary online viscometry in exclusion chromatography. The relationship between the detector response and pressure is linear, in agreement with the theoretically expected influence of pressure on refractive index and its dependence on temperature is negligible. Whole polymer and local intrinsic viscosities were determined and compared for narrow and, respectively, broad molecular weight distribution polymer samples. Considering that the detection system described can be improved, the results suggest that modern DRI detectors are susceptible to satisfy the requirements for a suitable pressure transducer in this application.

Flexomer™ Polyolefins-a Unique Class of Ethylene Copolymers for Low Temperature Film Applications

FLEXOMERTM polyolefins, referred to as very low density poly ethylenes (VLDPEs), are manufactured by a gas-phase, fluid bed process tech nology. Commercially available products typically range in density from 0.880 to 0.912 g/cc. The growing family of VLDPEs includes both narrow and broad molecular weight distribution polymers. The low crystallinity of these resins results in energy absorbing characteristics that yield outstanding low tempera ture impact properties. The lower brittleness temperature of VLPDE products provides superior low temperature performance when compared with ethylene vinyl acetate (EVA) and linear low-density polyethylene (LLDPE) copolymers.

Appraisal of a molecular weight distribution‐to‐rheology conversion scheme for linear polyethylenes

AbstractA theoretical scheme relating quantitatively the rheology of linear polymer melts to molecular weight distribution (MWD) would be of great significance in that it can help interpret polymer rheology and processing behavior in terms of molecular weight characteristics. The present paper is concerned with the appraisal of such a theory—the partition model of Bersted. The theory involves four parameters that are fitted to experimental data on a variety of linear polyethylenes. Although the model does fit the data with better than 10% accuracy, the parameters show some variability that points to theory limitations. An error analysis also shows that this variability is partly accounted for by experimental errors in MWD determination that are amplified in the predicted rheological properties. The rheological properties are shown to be heavily influenced by the high molecular weight tail of the MWD. Errors in MWD determination are detrimental for a MWD‐to‐rheology conversion, even if a conversion scheme were perfectly accurate. Low levels of long‐chain branching that may possibly be present are also detrimental to an MWD‐to‐rheology conversion. The inverse problem of determining the complete MWD from rheology appears to be practically infeasible for broad MWD polymers. © 1993 John Wiley & Sons, Inc.

Size Exclusion Chromatography/Differential Viscometry of Cationic Polymers

Abstract When employed as an on-line SEC detector, differential viscometry can be used to characterize the molecular weight distribution of water-soluble, cationic polymers. This technique is demonstrated using cationic poly(2-vinyl pyridine) for calibration of log(molecular weight ∗ intrinsic viscosity) versus retention volume, on SynChrom CATSEC columns in a mobile phase of 0.1% trifluoroacetic acid/0.20 N NaNO3 at 35° C. Characterization of broad molecular weight distribution polymers, such as poly(allyl amine), is presented based on universal calibration. Mark-Houwink constants and intrinsic viscosities are measured online for the standards, over a range of molecular weights from 2.90E3 to 1.00E6. Preliminary characterization of poly(2-vinyl pyridine) in THF under universal calibration conditions is also reviewed.

Correlation between the crossover modulus and the molecular weight distribution using the Doi-Edwards theory of reptation and the Rouse theory

The crossover modulus in the dynamic mechanical spectrum was linked with the molecular weight distribution (MWD) over a wide range of polydispersity ( $${{\bar M_w } \mathord{\left/ {\vphantom {{\bar M_w } {\bar M_n }}} \right. \kern-\nulldelimiterspace} {\bar M_n }}$$ = 1 to 6). Reasonable agreement was obtained between theory and experiment for near monodisperse and narrow MWD polymers using the Doi-Edwards theory of reptation. For broad MWD polymers, the Doi-Edwards theory was found to be inapplicable. Using the Doi-Edwards theory for the shorter chains and a Rouse type mechanism for the longer chains, a good fit was obtained between the calculated and experimentally measured crossover modulus values.

Molecular weight – viscosity relationships for a broad molecular weight distribution polymer

A novel and simple method is described for evaluation of molecular weight – viscosity relationships for a polymer where only broad molecular weight distribution samples are available. The method demands measurement of the intrinsic viscosity and GPC chromatograms of several samples. Results of applying the procedure to bisphenol A – Diethyleneglycol (50:50) copolycarbonate are presented.

Partitioning of polystyrene between incompatible phases and distributional effects in the system polystyrene–polybutadiene–toluene

AbstractThe average molecular weights and the molecular weight distributions of polystyrene (PS) in the conjugate incompatible phases of the ternary system of PS and polybutadiene with toluene as solvent were studied at 23°C. Gelpermeation chromatography, with ultraviolet and differential refractive index detectors, was used for analyzing the compositions of the conjugate phases and for obtaining the molecular weight averages of PS in the phases. Both narrow and broad molecular weight distribution (MWD) polymer samples were used. The effect of broad MWD polymers is seen as one of narrowing the shape of the binodal, thus effectively increasing the compatible region. The molecular weight averages of PS in the two conjugate phases do not vary significantly in the case of the narrow MWD PS sample while for broad MWD samples the average molecular weight of PS is found to be higher in the PS‐rich phase than in the polybutadiene‐rich phase for tie lines closer to the plait point indicating a partitioning or redistribution of the molecular weight species of PS between the incompatible phases.

A gel permeation chromatography calibration method for a broad molecular weight distribution polymer

Journal of Applied Polymer ScienceVolume 22, Issue 2 p. 597-597 ErratumFree Access A gel permeation chromatography calibration method for a broad molecular weight distribution polymer H. K. Mahabadi, H. K. Mahabadi Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, CanadaSearch for more papers by this authorK. F. O'Driscoll, K. F. O'Driscoll Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, CanadaSearch for more papers by this author H. K. Mahabadi, H. K. Mahabadi Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, CanadaSearch for more papers by this authorK. F. O'Driscoll, K. F. O'Driscoll Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, CanadaSearch for more papers by this author First published: February 1978 https://doi.org/10.1002/app.1978.070220229Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume22, Issue2February 1978Pages 597-597 RelatedInformation

A gel permeation chromatography calibration method for a broad molecular weight distribution polymer

AbstractA novel, precise, and simple method is described for developing a GPC calibration curve for a polymer where only broad molecular weight distribution samples are available. The method demands a GPC calibration curve for another polymer (e.g., polystyrene) and measurement of the intrinsic viscosity and an average molecular weight for each of several samples of the broad molecular weight distribution polymer in addition to GPC measurements on those samples. Results of applying the procedure to poly(n‐lauryl methacrylate) are presented.