Effect of the Z‐ and Macro‐R‐Group on the Thermal Desulfurization of Polymers Synthesized with Acid/Base “Switchable” Dithiocarbamate RAFT Agents

Abstract

Thermolysis is examined as a method for complete desulfurization of reversible addition-fragmentation chain transfer (RAFT)-synthesized polymers prepared with acid/base "switchable" N-methyl-N-pyridyldithiocarbamates [RS CZ or RS CZH ]. Macro-RAFT agents from more activated monomers (MAMs) (i.e., styrene (St), N-isopropylacrylamide (NIPAm), and methyl methacrylate (MMA)) with RS CZH and less activated monomers (LAMs) (i.e., vinyl acetate (VAc) and N-vinylpyrolidone (NVP)) with RS CZ are prepared by RAFT polymerization and analyzed by thermogravimetric analysis. In all cases, a mass loss consistent with loss of the end group (ZCS H) is observed at temperatures lower than, and largely discrete from, that required for further degradation of the polymer. The temperatures for end group loss and the new end groups formed are strongly dependent on the identity of the R(P) and the state of the pyridyl Z group; increasing in the series poly(MMA) < poly(St) ∼ poly(NIPAm) << poly(VAc) ∼ poly(NVP) for S CZ and poly(MMA) < poly(St) ∼ poly(NIPAm) for S CZH . Clean end group removal is possible for poly(St) and poly(NVP). For poly(NIPAm), the thiocarbonyl chain end is removed, but the end group identity is less certain. For poly(MMA) and poly(VAc), some degradation of the polymer accompanies end group loss under the conditions used and further refinement of the process is required.

Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions

“…That is to say, the measurement y i (t i j ) arrived at t i j reflects the value of x i M at time t i j − δ i j . The proposed observer for the system (6) with multiple measurement delays is based on the multi-rate observer design (7) combined with dead time compensation. When the sampled measurement arrives at t i j after a delay δ i j , a dead time compensator would be initiated to recalculate the past estimates for t ∈ [t i j − δ i j , t i j ] with the following observer design [55]:x…”

“…After the dead time compensation has updated the past estimates, the inter-sample prediction will be applied for the missing points between two measurements for t ∈ [t i j , t i j ] in the same spirit as the delay-free multi-rate observer (7). If a measurement is available at t i j without any delay, then no dead time compensation is needed and the inter-sample prediction runs immediately after reset.…”

“…where w(t) is calculated from both the dead time compensator (9) and the inter-sample predictor (7). Figure 1 depicts the two-step estimation process from time t 0 .…”

“…This step makes use of the available measurements in the delay-free observer, in the same order as they are sampled. As a second step, the updated estimates are used as the initial condition for the observer coupled with inter-sample output predictors (7) at t N MR n . In addition, this multi-rate multi-delay observer now works like a delay-free multi-rate observer with no delayed measurement, until the next measurement from SEC becomes available at t N MR n+1 .…”

Ab initio RAFT emulsion polymerization mediated by small cationic RAFT agents to form polymers with low molar mass dispersity

“…The (pyridin-4-yl)carbamodithioates 1 were initially designed for use as switchable RAFT agents that can provide good control over both more and less activated monomers (MAMs and LAMs). [40][41][42][43][44][45][46][47][48][49] In their switched or protonated state, 2, they allow the synthesis of low Ð m poly(MAM)s, e.g., polystyrene with 4, and in their unswitched or neutral state, 1, facile polymerization of LAMs to give low Ð m poly(LAM)s, e.g., poly(VAc) with 3. These RAFT agents also enable the preparation of low Ð m poly(MAM)-block-poly(LAM)s by sequential monomer addition.…”