Table 5.
Polymerization of rac‐lactide in solution and bulk using [Zn(TMGhydroqu)2](OTf)2 (C6).[a]
|
Entry |
[M]/[I] |
kapp [b] [s−1] |
t [s] |
Conv.[c] [%] |
M n,theo. [d] [g mol−1] |
M n [e] [g mol−1] |
Ð [e] |
|---|---|---|---|---|---|---|---|
|
1 |
1250 : 1 |
0.0451 |
165 |
90 |
162000 |
58100 |
1.5 |
|
2 |
1500 : 1 |
0.0285 |
161 |
53 |
115000 |
89000 |
1.4 |
|
3 |
2000 : 1 |
0.0028 |
345 |
38 |
110000 |
72500 |
1.5 |
|
4 |
2500 : 1 |
0.0009 |
885 |
31 |
– |
– |
– |
|
5[f] |
2500 : 1 : 10 |
0.0178 |
285 |
95 |
34200 |
33000 |
1.3 |
|
6[g] |
2500 : 1 |
0.0326 |
285 |
94 |
339000 |
71400 |
1.8 |
|
7[f,g] |
2500 : 1 : 1 |
0.0551 |
285 |
96 |
346000 |
83500 |
1.4 |
|
8[h] |
500 : 1 |
0.0023 |
660 |
61 |
44000 |
54000 |
1.4 |
|
9[h] |
600 : 1 |
0.0014 |
660 |
37 |
32000 |
29000 |
1.5 |
|
10[h] |
750 : 1 |
0.0012 |
660 |
48 |
n. d. |
n. d. |
n. d. |
|
11[h] |
800 : 1 |
0.0010 |
660 |
41 |
n. d. |
n. d. |
n. d. |
[a] Conditions in bulk: non‐purified technical grade rac‐lactide, 150 °C, stirrer speed: 260 rpm. [b] The rate constant k app was determined by plotting ln([LA]0/[LA]t) vs. t. [c] Determined by 1H NMR spectroscopy. [d] Theoretical number‐average molar mass calculated by conversion×molar mass×[M]/[I]. [e] Determined via GPC analysis in THF. Mn : determined number‐average molar mass; Ð: polydispersity obtained by Mw /Mn . [f] Co‐initiator: benzyl alcohol. [g] Sublimated lactide. [h] Using c(lactide)=1.0 mol L−1 at 100 °C in toluene. n. d.=not determined.