Method for removing sulfur-containing end groups
View Patent ↗This invention provides a method for removing certain sulfur-containing groups from polymers, especially those made via RAFT polymerization processes.
1. A process for replacing a functional group, —SC(S)X, with —H, comprising contacting a polymer containing a functional group, —SC(S)X with a salt of hypophosphorous acid and a radical initiator, wherein
X is R, OR 1 , N(R 2 ) 2 , SR 3 , or P(O)(OR 4 ) 2 ;
R is substituted or unsubstituted C 1 -C 25 alkyl; substituted or unsubstituted C 2 -C 25 alkenyl; substituted or unsubstituted C 2 -C 25 alkynyl; substituted or unsubstituted phenyl; substituted or unsubstituted naphthyl; and substituted or unsubstituted benzyl; and
R 1 , R 2 , R 3 , and R 4 are substituted or unsubstituted C 1 -C 25 alkyl; substituted or unsubstituted C 6 -C 10 aryl; a 3- to 8-membered carbocyclic or heterocyclic ring, or N(R 2 ) 2 is a 3- to 8-membered heterocyclic ring.
2. The process of claim 1 , wherein the salt of hypophosphorous acid is a mono-, di-, tri-, or tetra-alkylammonium salt of hypophosphorous acid.
3. The process of claim 1 , wherein the salt of hypophosphorous acid is a triethylammonium, tetrabutylammonium, Dabco, or N-ethylpiperidinium salt of hypophosphorous acid.
4. The process of claim 1 , wherein the salt of hypophosphorous acid is formed in situ through the reaction of a nitrogen base with hypophosphorous acid.
5. The process of claim 1 , wherein X is R, and R is selected from the group of substituted or unsubstituted C 1 -C 25 alkyl; substituted or unsubstituted C 2 -C 25 alkenyl; substituted or unsubstituted C 2 -C 25 alkynyl; substituted or unsubstituted phenyl; substituted or unsubstituted naphthyl; and substituted or unsubstituted benzyl.
6. The process of claim 1 , wherein X is OR 1 , and R 1 is selected from the group of substituted or unsubstituted C 1 -C 25 alkyl; substituted or unsubstituted phenyl; pentafluorophenyl; and substituted or unsubstituted naphthyl.
7. The process of claim 1 , wherein X is N(R 2 ) 2 , and N(R 2 ) 2 is selected from the group of substituted or unsubstituted dimethylamine, diethylamine, dipropylamine, dibutylamine, pyrrolidyl, imidazolinyl, pyrrolidonyl, and phthalimidyl.
8. The process of claim 1 , wherein X is SR 3 , and R 3 is selected from the group of substituted or unsubstituted C 1 -C 25 alkyl; substituted or unsubstituted benzyl; and substituted or unsubstituted phenyl.
9. The process of claim 1 , wherein the polymer comprises repeat units derived from a group consisting of acrylates, methacrylates, and styrenes.
10. The process of claim 1 , wherein the polymer is produced by a RAFT polymerization process.