Analysis of Star-Branched Polymers with Triple Detection (Refractive Index, Viscometry, Light Scattering) Gel Permeation Chromatography

Abstract

This paper deals with the characterization of star-branched model copolymers. The polymer branches are composed of PMMAPtBuA di-block copolymers of poly(methy1 methacrylate) and poly(rert-butylacrylate) with well-controlled chemical composition and structure (very low polydispersity). When these copolymer branches are chemically coupled, they produce star-branched copolymers with various numbers of branches. Number-average molecular weights Mn of stars and branches were used to calculate the number of branches of the starbranched copolymers. In order to determine the real structure of the star-branched copolymers, we have measured the branching parameter g' and tested several hypothesis on the relationship which links the number of branches to the branching parameter g. The value of the exponent of the g/g'relationship. which characterizes the type of branching, was determined at several conditions. Values were dependent on the branching relationship, however, it was not possible to find an exponent value of 0.5, corresponding to pure star-branched molecules. We could not conclude whether or not the technique of multidetection GPC was not accurate enough to obtain this kind of infomation or if the studied star-branched copolymers had a complex structure, more complicated than a simple star. Excellent agreement was found between light scattering values and from viscometry with universal calibration. These results demonstrate excellent performance for universal calibration, even for highly branched polymers with unusual viscometric behavior.

One-Pot Synthesis of Star-Shaped Macromolecules Containing Polyglycidol and Poly(ethylene oxide) Arms

“…The experimental points from two series of experiments are on the common line, as it was observed previously for star polymers with PEO arms . The determined value of the slope x = 0.737 is slightly lower than that previously reported by us for PEO stars: x = 0.818 (ref ) and by Lesec et al ( x = 0.87) for star-shaped macromolecules obtained in the coupling reaction of diblock macromonomers (copolymers) poly(methyl methacrylate)−poly( tert -butyl acrylate) with ethhylene glycol dimethacrylate . This value indicates that structures of stars, both the first and the second generation, are closer to the regular stars than to the highly branched and/or comblike polymers.…”

“…A simple relationship between branching indexes 〈 g 〉 and 〈 g ‘ 〉 (cf. eq 6 and 7) is known: where the exponent x depends on the macromolecular architecture: x = 0.5 for regular stars, x = 1.5 for comblike branched polymers, and, therefore, for stars of intermediate branching x is between these two values . In Figure the dependence of log 〈 g ‘ 〉 on log 〈 g 〉 is given.…”

Reaction of oligoalcohols with diepoxides: An easy, one‐pot way to star‐shaped, multibranched polymers. II. Poly(ethylene oxide) stars—synthesis and analysis by size exclusion chromatography triple‐detection method

“…The determined value of the slope x = 0.818 indicates that structures of stars, both first and second generation, are closer to the regular stars than to highly branched irregular stars (with a high distribution of the arms' length). The value of x = 0.87 was reported by Lesec and Milléquant38 for star‐shaped macromolecules obtained in coupling reaction of diblock macromonomers (copolymers) poly(methyl methacrylate)‐Pt‐BuA with ethylene glycol dimethacrylate. The two methods of synthesis—Lesec's and that described in this article—have much in common; therefore, the stars' architectures could be close one to another.…”

“…Second, it is believed that the relationship between g ′ and g could give some additional information on the actual structure of the star‐shaped macromolecules. This relationship between both branching indices, namely, determined from R g ( g ) and the limited viscosity number ( g ′) reads where exponent x depends on macromolecular architecture: x = 0.5 for regular stars and x = 1.5 for comblike branched polymers, and therefore for stars of intermediate branching x is between these two values 38. In Figure 12, the dependence of log g ′ on log g is given for our stars; the experimental points from three series of experiments are on the common line.…”

Synthesis and Characterization of Star Polymers with Varying Arm Number, Length, and Composition from Organic and Hybrid Inorganic/Organic Multifunctional Initiators

“…Molecular weight analysis was calculated with PSS software; calibration based on low polydispersity polystyrene standards for styrene and acrylate polymerizations and PMMA standards for reactions with MMA. Triple detection SEC (3D-SEC) was measured in THF using a Spectrasystem P1000 chromatograph pump equipped with PSS (1000 Å, 10 5 Å, and 10 6 Å) and Phenomenex (guard) columns in series with a Wyatt Minidawn light-scattering detector operating at 90° then in parallel with a Waters 410 differential refractometer and a Viscotek T50 intrinsic viscometer. Data acquisition and analysis were performed with PSS software.…”