Tetrabutylphosphonium bromide (TBPB) was used to catalyze several polyesterifications of 3,3’ dithiopropionic acid with four different diepoxides and using gallic acid to terminate the polymer/oligomer.
We speculate that TBPB was chosen for several reasons. The first is that TBPB provides an organic- soluble source of bromide (not classical PTC) that initiates the ring opening of the epoxide that facilitates the esterification with the acid. A second reason is that the reaction undergoes significant heat history at 105 deg C over 24 hours in all four polyesterifications and quaternary ammonium salts, such as TBAB, are not as stable as quaternary phosphonium salts such as TBPB. Of course, “P-quats” are more expensive then “N-quats”, so it is beneficial to choose a P-quat that is not overly expensive. TBPB has a lower molecular weight than other P-quats, so the cost per mole of P-quat might be acceptable.
The polymers appear to have weight average molecular weights that represent 4-6 repeat units, so these may be considered to be oligomers depending on how you define oligomers versus polymers.
These polyesters are useful in protective films for the lithography process in the production of semiconductor chips.
About Marc Halpern
Dr. Halpern is founder and president of PTC Organics, Inc., the only company dedicated exclusively to developing low-cost high-performance green chemistry processes for the manufacture of organic chemicals using Phase Transfer Catalysis. Dr. Halpern has innovated PTC breakthroughs for pharmaceuticals, agrochemicals, petrochemicals, monomers, polymers, flavors & fragrances, dyes & pigments and solvents. Dr. Halpern has provided PTC services on-site at more than 260 industrial process R&D departments in 37 countries and has helped chemical companies save > $200 million. Dr. Halpern co-authored five books including the best-selling “Phase-Transfer Catalysis: Fundamentals, Applications and Industrial Perspectives” and has presented the 2-day course “Practical Phase-Transfer Catalysis” at 50 locations in the US, Europe and Asia.
Dr. Halpern founded the journal “Industrial Phase-Transfer Catalysis” and “The PTC Tip of the Month” enjoyed by 2,100 qualified subscribers, now beyond 130 issues. In 2014, Dr. Halpern is celebrating his 30th year in the chemical industry, including serving as a process chemist at Dow Chemical, a supervisor of process chemistry at ICI, Director of R&D at Sybron Chemicals and founder and president of PTC Organics Inc. (15 years) and PTC Communications Inc. (20 years). Dr. Halpern also co-founded PTC Interface Inc. in 1989 and PTC Value Recovery Inc. in 1999. His academic breakthroughs include the PTC pKa Guidelines, the q-value for quat accessibility and he has achieved industrial PTC breakthroughs for a dozen strong base reactions as well as esterifications, transesterifications, epoxidations and chloromethylations plus contributed to more than 100 other industrial PTC process development projects.
Dr. Halpern has dedicated his adult life to his family and to phase-transfer catalysis (in that order!).
