Accumulated Molecular Weight Distribution

In a deterministic approach, the instantaneous MWDs are calculated first, and then the accumulated MWD is obtained by integrating the instantaneous MWDs. However, in MC simulations, we can follow the reaction history of each polymer particle directly, and the full MWD is obtained by simulating a large number of polymer particles [263]. Therefore, highly complex reaction kinetics can be simulated directly in a straightforward manner. 

The parameter K shown in the figure represents the reactivity of the terminal double bonds, defined by K=k lk, and k is the rate constant of TDBP. The 

---

This can be accumulated in a similar manner to that of instantaneous molecular weight distributions (11, 8) ... 

FIGURE 2 Degradation of pullulan (MW 200,000) in replicate anaerobic enrichment cultures of marine bacteria from anoxic sediments. Open circles show total pullulan concentrations remaining in the medium at each time point. The molecular weight distribution of the pullulan is shown by the stacked bars white >10,000 Da, stripes 5000 Da, black <1200 Da. Note that the lower molecular weight fraction progressively accumulated between 50 and 64 h. [Data from Arnosti et al. (1994).]... 

Cationic polymerization was performed in a microreaction system consisting of two micromixers coimected by microcapDlaries [4]. A method that used irreversible generation and accumulation of highly reactive cations in the absence of nucleophile was apphed for polymerization. The molecular weight distribution was controlled by extremely fast micromixing, and the resulting polymer could be used for followup reactions. 

Because untreated ethylene is recycled, impurities may accumulate in the system that may affect the overall production of the primary radicals and the molecular-weight developments of the polyethylene product. Chain transfer agents such as ketones, aldehydes, alcohols, hydrogen, or chlorinated components may be added to narrow molecular-weight distribution. 

Polymerization of vinyl ethers initiated by an A -acyUminium ion pool has demonstrated that the molecular weight and the molecular weight distribution can be controlled by using the flow microreactor system (Fig. 10.5) [4, 5]. An iV-acyh-minium ion generated and accumulated by the cation pool method was used as an initiator, which was mixed with a vinyl ether at high speed using a micromixer. The polymerization proceeded in a flow microreactor and was complete within a short residence time. An amine was then introduced using a micromixer to terminate the polymerization. Thus, this polymerization can be called flash polymerization. 

---