The previously described microgel synthesis in which living poly(4-tert-butylstyrene) was reacted with 1,4-divinylbenzene was studied. Samples were taken after the addition of the crosslinker and characterized by gel-permeation chromatography (GPC) with an on-line multi angle laser light scattering (MALLS)-and a differential refractive index (DRI) detector. Primary particle formation was found early in the reaction followed by interparticular crosslinking. The GPC calibration curves allowed the derivation of a branching plot. The branching plots showed, that in addition to interparticular crosslink reactions also intraparticular crosslink reactions are occurring. The plots also showed that the primary particles scale like linear polymers, which led to the conclusion that they consist of comb-like structures with poly(4-vinylstyrene) as the backbone and poly(4-tert-butylstyrene) as branches.
A new method combining thermal field-flow fractionation (ThFFF) and SEC−MALLS is
proposed for the measurement of the thermal diffusion coefficient D
T for polydisperse polymeric samples.
This method should greatly increase the range of applicability of ThFFF for characterization of block
copolymers and also for studies of thermal diffusion, an interesting phenomenon not yet well understood.
ThFFF is one of only a few techniques (e.g., thermal diffusion forced Rayleigh scattering) that can
determine D
T values of polymers. The values of D
T can be used to reflect the surface composition of
block copolymer molecules as reported in recent studies. Currently, the value has been measured with
ThFFF based on the sample peak maximum method, which can introduce errors when the sample has a
broad MW distribution. The method proposed here measures D
T by taking all digitized points in the
entire sample peak into consideration, and has been tested with polystyrene, poly(tert-butylstyrene), and
some copolymer microgels. Preliminary results are presented and discussed.
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