PLP-SEC experiments

Propagation rate coefficients for styrene, vinyl acetate, and various acrylates and methacrylates were determined by the so-called PLP-SEC technique, which combines pulsed-laser-initiated polymerization (PLP) with subsequent polymer analysis via size-exclusion chromatography (SEC). The PLP-SEC experiment measures the product of propagation rate coefficient, kp, and monomer concentration, Cm ... 

Equation (5), in which Cm and cr are the monomer concentration and the pulse-induced initial radical concentration at t=0, respectively, is used for fitting the experimental monomer concentration vs time traces to yield the parameters (kt)/kp and (kt) Cr. If kp is known from independent PLP-SEC experiments, (kt) is obtained as a function of monomer conversion from successive SP-PLP ex-... 

Variation of kp for methaciyllc acid In aqueous solution as a function of monomer concentration, Cmaa- The data Is from aqueous-phase PLP-SEC experiments at 60 °C tabulated In Ref. 

Because of solubihty restrictions, PLP-SEC experiments on aqueous solutions of MAA at concentrations above 40 wt.-% and a approaching unity were not successful so far. Within further experiments... 

In order to deduce PLP-SEC-based information on the dependence of kp on monomer conversion, the present study addresses kp measurements for MAA in the presence of poly(MAA) and of iso-butyric acid (IBA). The latter component represents the saturated analogue of MAA and thus may be looked upon as the associated polymer of chain length unity . The PLP-SEC experiments have been carried out at 25 °C and ambient pressure on aqueous MAA solutions to which different amounts of poly(MAA) or of IBA have been added. The mixtures were prepared such that the overall concentration of carboxylic acid, irrespective of the COOH groups being part of the monomer, the polymer, or the wo-butyric acid, is fixed at 20 wt.-%. Within each PLP-SEC experiment, only a small fraction of the MAA is polymerized, such as to obtain an amount of PLP-induced poly(MAA) which is sufficient for SEC analysis. 

Within the PLP-SEC experiments on non-ionized MAA in the presence of poly(MAA), the determination of points of inflection, via the maxima in the associated first-derivative curves of the MWD, is complicated by the pre-mixed polymer which obviously can not be removed prior to SEC analysis. Figures 2 and 3 depict MWDs (A) and the associated first-derivative curves (B) of polymer samples obtained by PLP-induced polymerizations of 15 wt.-% MAA dissolved in water containing 5 wt.% of pre-mixed polymer and of 10 wt.-% MAA dissolved in water containing 10 wt.-% of pre-mixed polymer, respectively. The full lines (a) represent the polymer sample after pulsed laser polymerization, whereas the dashed... 

The triangles refer to PLP-SEC experi- conversion thus is made up of a conversion ... 

Fig. 14. Typical data sheet detailing the outcome of a successful PLP-SEC experiment for a styrene bulk pol3rmerization at 25"C.

Arzamendi G, Plessis C, Leiza JR, Asua JM. Effect of the intramolecular chain transfer to polymer on PLP/SEC experiments of alkyl acrylates. Macromol Theory Simul 2003 12 315-324. 

Table 5 Activation volumes AlA(/rp) deduced from PLP-SEC experiments for methacrylates and styrene at 30 °C, for MA at-15X, and for DAat15°C ...

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