Page 49 - Biodegradable Polyesters

2.2 Radical Ring-Opening Polymerization (RROP) of Cyclic Ketene Acetals 27

2-methylene-1,3-dioxepane. Till date, synthetic recipes for making a large num-
ber of structurally different CKAs are available (Chart 2.1) and they are stable for
a long time if protected from moisture and air [12, 14, 15].

O
O O
O O O O O
C
H 3 CH 3
2-Methylene-4-phenyl-1,3- 5,6-Benzo-2-methylene- 2-Methylene-1,3- 4,7-Dimethyl-2-methylene-
dioxalane 1,3-dioxepane dioxepane 1,3- dioxepane
O
O O O O O
O
O
C 6 H 13 / C 10 H 21
2-Methylene-4-hexyl/decyl-1,3- 2,5-Dimethylene- 2,4-Dimethylene- 2-Methylene-1,3-dioxe
dioxalane 1,3-dioxane 1,3-dioxalane -5-pene
O O
O
O O O O
O
O
2-Ethylidene-1,3- 1-Vinyl-4,7-dioxaspiro[2,4] O 3,9-Bis-methylene-
dioxane heptane 2,4,8,10-tetraoxa-spiro
Ph [5,5]undecane
O O
O O O O
1-Vinyl-5-phenyl-4,7- 1-Vinyl-4,9-dioxaspiro- 4-Phenyl-2-propenylene- 2-Methylene-1,3-
dioxaspiro[2,4]heptane [2.6]nonane 1,3-dioxalane dioxalane
O
O
O O O
O O O O O
O O O CH / C H 5
3
2
R
2
R 1
9,9-Disubstituted-4-methylene- 2-Methylene-1,3,6- 2,5-Methylene -1,3- 2-Ethylidene-4-methyl/ethyl-
3,5,8,10-tetraoxabicyclo trioxocane dioxane 1,3-dioxalane
[5.3.0]decane
CF CF CF
CF 2 2 2 2
O O O O O O O O
F 2 C CF 2 F C CF 2
2
C
CF
F 2 3
Perfluoro-2-methylene- 2-Difluoromethylene- Perfluoro-2-methylene-4-methyl- 2-Difluoromethylene-
1,3-dioxane 1,3-dioxane 1,3-dioxolane 4-methyl-1,3-dioxolane
O
CF 2
O O
O
2-Difluoromethylene- 1-Vinyl-6,7-benzo-4,9-
1,3-dioxolane dioxaspiro[2.6]nonane
Chart 2.1 A wide variety of cyclic ketene acetals are available in the literature undergoing
radical ring-opening polymerization for the formation of polyesters. CKAs studied in details
in literature are presented here with their names and structures [12].