Radical telomerization of 1,3-butadiene with perfluoroalkyl iodides

Use of Originalω-Perfluorinated Dithioesters for the Synthesis of Well-Controlled Polymers by Reversible Addition-Fragmentation Chain Transfer (RAFT)

“…The main difficulty was to find out the best temperature comprise for the RAFT polymerization of butadiene. Ideally, poly(butadiene) required to be telomerized at 140-150 8C in solution to reach high conversions (typically 60-70%) [35] or polymerized at least above 130 8C (Table 2 -E18). These temperatures are however too high to prevent dithioesters from thermal degradation (an elimination of CS 2 was noted).…”

“…[34] Telomerization of 1,3-butadiene with perfluoroalkyl iodides also led to fluorinated diblock cotelomers. [35] However, because of the high transfer constant of perfluoroalkyl iodides towards 1,3-butadiene (C tr = 2.59), only 50-60 mol-% of the resulting telomers contained a fluorinated moiety. In addition, it should be noted that perfluoroalkylsulfonyl chlorides and bromides have initiated metal catalyzed radical polymerization of styrene or MMA to afford polymers with perfluoroalkyl end-groups, via a living process.…”

Instructions for use: Instructions for whom?

“…This enabled us to monitor the telomerization and led to the conversion–time profiles. Final conversion values, calculated by this method were slightly higher (2–10%) than those calculated by eq 1 because it takes into account the amount of 1,3‐butadiene converted in its dimerization product (i.e., 4‐vinyl‐cyclohexene), as shown in a previous article 4…”

“…of a telomer (average number of butadiene units per polymeric chain) can be calculated with its 1 H NMR spectrum according to eq 3. h i stands for the integration of the proton i ( i = a, b, or c), and the calculation of is as follows, as demonstrated in a previous article:4 If the functionality of the telomers ( f ), as defined later, is close to unity, calculated by eq 3 can be then considered the real average chain length of the telomer. As an example, if a product contains 50 mol % functional telomers ( f = 1) with an average chain length of 20 and 50 mol % nonfunctional telomers ( f = 0) with an average chain length of 200, the value, calculated by eq 3 will be 220.…”

“…In the first method, Then, In the second method, A third method has also been used and is based on 1 H NMR spectrum analysis (integrated area). It is explained in our previous work 4…”