Synthesis and Characterization of Comb-Shaped Polymers by SEC with On-Line Light Scattering and Viscometry Detection

Abstract

Comb-shaped polystyrenes with UV-labeled side chains were synthesized and analyzed by SEC with on-line light scattering and viscometry detection. The introduction of the UV label allows for a model-independent determination of the number of grafts within each SEC slice and therefore the calculation of the expected contraction factors, g = 〈R g , br 2〉/〈R g ,lin 2〉 and g ‘ = [η]br/[η]lin. Using molecular weight sensitive detectors, the contraction factors were determined experimentally and compared to the expected ones. It was found that the experimentally determined g values are larger than the ones calculated on the basis of the Gaussian chain assumption. Therefore, the calculation of the number of branches based on theoretically expected contraction factors is not feasible. Attempts to include corrections for excluded-volume effects failed. For the exponent ε of the relationship g‘ = g ε a value close to ε = 1 was found, in contradiction with the expectations from the Flory−Fox and Zimm−Kilb relations. It was observed that the intrinsic viscosities of the combs are close to the intrinsic viscosities of the parent backbone polymer itself, allowing to use this empirical relationship for the determination of the amounts of grafts present in the polymer.

Transfer to Polymer and Long‐Chain Branching in PLP–SEC of Acrylates

“…Current knowledge is insufficient to determine the amount of long-chain branches per chain for statistically branched polymers such as our polyacrylates. [26,42,43] …”

Anionic Synthesis and Rheological Characterization of Poly(p‐methylstyrene) Model Comb Architectures with a Defined and Very Low Degree of Long Chain Branching

“…[16,21] By the use of PpMS as a comb backbone the number of branching points can be well controlled by selective bromination [34,35] of the methyl group and degrees of functionalization of less than 1 mol-% (e.g., 1 branch per 200 backbone C-atoms) can be achieved. Because of its similarity to styrene, p-methylstyrene allows the independent synthesis of the backbone and side chains with well defined molecular weights and low polydispersities by anionic polymerization.…”

Polymerization of Styrene Sulfonate Ethyl Ester and Styrene Sulfonate Dodecyl Ester by ATRP: Synthesis and Characterization of Polymer Brushes

“…The literature reports that the bromine contents determined by NMR spectroscopy are lower than expected. [33,40] However, the conclusion that bromination is incomplete seems to be erroneous in the light of the values determined by elemental analysis. These values have been cross-checked by independent carbon and hydrogen determination, and yield comparable results for the remaining bromine content.…”

“…In previous work on polymer brushes, the Kuhn segment length has been determined from the plot of R g vs M w for each GPC-MALLS slice. [40] As pointed out by Wahnes, this is only possible for samples with broad backbone polydispersities and was, therefore, not done for these samples. [9] In Figure 10c the radii of gyration of the entire sample (summation over all slices) are plotted versus the grafting density of the sample.…”

“…[10] It has been confirmed by small-angle X-ray scattering (SAXS), [11] atomic force microscopy (AFM), [12] and rheology [13] that polymer brushes are not entangled in the bulk state. Polymer brushes can be obtained by the following synthetic strategies, as described in the literature: by the 'grafting onto' approach [14][15][16][17] (for non-polar monomers), the 'grafting from' or 'macroinitiator approach' [18][19][20][21][22][23] (for acrylates, methacrylates, styrenes, acrylamides and, only very recently, polypeptides and sugars), and the 'grafting through' or 'macromonomer approach'. [24][25][26][27][28][29] The aim of our work is the synthesis and characterization of cylindrical polyelectrolyte brushes from styrene sulfonate using the corresponding styrene sulfonate ester brushes as precursors.…”