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α
-chloro-
ε
-caprolactone, a versatile precursor
for grafting of aliphatic polyesters
Raphaël Riva, Sandrine Lenoir, Philippe Lecomte,
Christine Jérôme
raphael.riva@ulg.ac.be, University of Liège,Sart-Tilman, B6a, B-4000 Liège
Cl O O O Cl O O O Cl O 4 n 5 mx O O O O O O 4 n 5 m x Cl R R O O O O 4 n 5 mx PEO Cl O O PEO Oxidation Ring-opening copolymerization Commercially
available Yield = 75% Transition metal
complex
Olefin Time Conversion But-3-enyl benzoate 24 h 51%
But-3-en-1-ol 8 h 37 % Vinylacetic acid 24 h 32 % 1,2-epoxyhex-5-ene 8 h 42 %
Metal transition
complex Solvent T° Time Conversion
CuCl/HMTETA Toluene 60°C 48 h 0 % CuBr/HMTETA Toluene 60°C 48 h 0 % NiBr2(PPh3)2 Toluene 60°C 48 h 0 %
CuBr/HMTETA DMF 60°C 8 h 51 %
CuBr/Me6-Tren DMF 60°C 1 h > 95 %
Table 1 : Influence of the solvent and the transition metal complex on the addition of but-3-enyl benzoate. Conversion measured by 1H NMR analysis
Table 2 : ATRA for the different olefins by using CuBr/HMTETA in DMF.
Atom Transfer Radical Addition (ATRA)
% of αClεCL MnPEO % of addition % of PEO in the copolymerMw/Mn 10 350 g/mol > 90 25 1,5 10 750 g/mol 55 37 1,3 35 750 g/mol 57 49 1,7
Size of the particules in nm
10 100 1000 R e la ti v e i n te n si ty 0 20 40 60 80 100 OH OH O O
But-3-en-1-ol Vinylacetic acid 1,2-epoxyhex-5-ene
Abstract: Macromolecular engineering is one of the most powerful tool to synthesise many polymers of various architectures and with tailored properties. This contribution aims at reporting on a novel strategy for the macromolecular engineering of poly-ε-caprolactone (PCL) which is based on the use of a dual monomer / initiator compound, α-chloro-ε-caprolactone (αClεCL).
Formation of spherical micelles in aqueous solution
Table 3 : Influence of the molecular weight of PEO and the composition of the grafted copolyester on the % of addition.
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O O O PMMA O 4 n 5 m x O O O Cl O 4 n 5 m x O O Transition metal complexAtom Transfer Radical Polymerisation (ATRP)
a : Theor. Mn= [n MMA/ n poly(αClεCL)] . % conversion.
b, d : for the graft copolymer (PMMA calibration). c, e : for the PMMA grafts PMMA (PMMA calibration). f = initiation efficiency.
Theor. Mna
PMMA grafts MnbSEC MncSEC
Mw/Mnd SEC Mw/Mne SEC f 10500 72000 19000 2,0 2.3 0.6 8500 80000 28000 1.5 1.4 0.3 16000 94000 39100 1.8 1.4 0.4
The PMMA grafts have been collected after the degradation of poly(εCL) by a mixture of 1,4-dioxane / HCl 37 % (95/5) at 85°C for 32 hours.
Table 4 : SEC analysis of graft copolymers before and after degradation of poly(εCL).
SEC chromatograms before and after the degradation of the poly(εCL)
O O O Cl 4 O 5 n mx O O O 4 O 5 n mx N3 NaN3 DMF O O O 4 O 5 n mx N N N O Br O O Br O Click chemistry PCL-g-PS Graft copolymer CuCl/CuCl2/HMTETA CuBr/Me6-Tren O O Cl 3 O O O O Me p O O O O n m 3 3 px Cl Cl l Ph Ph O O Cl 3 O O O O n m 3 3 px O O O O Me p DMF 110°C, 24h
Synthesis of an heterografted PCL
Combination of ATRA and ATRP
No quantitative ATRA of PEO
20 22 24 26 28
Elution Time (min)
SEC chromatograms for poly(εCL-g-EO)and
poly((εCL-g-EO)-co-(εCL-g-styrene))
Click chemistry
Improvement of the initiation efficiency by the grafting of an activated bromide The PS grafts have been collected after the degradation of poly(εCL)
by a mixture of 1,4-dioxane / HCl 37 % (95/5) at 85°C for 72 hours. After 6 h of polymerization, the conversion of styrene is equal to 52%
DP PS,total (1H NMR) DP PS, graft (SEC) Mw/Mn PS graft (SEC) ngraft by PCL chain nαclεCL Initiation efficiency 230 25 1.3 9 9 1
Table 5 : Results of the synthesis of PCL-g-PS graft copolymer
Conclusion : Various functionalized and graft copolyesters can be easily prepared from one functionalized lactone, the αClεCL . Several functions can be grafted by ATRA ontoαClεCL containing chains without significant degradation. Grafted PCL are also rapidly prepared by the initiation of the polymerization of vinyl monomers either from the pendant chloro atoms of the copolyester, either from pendant bromide introduced onto the copolyester by “click chemistry”. ATRA of PEO chains on a poly(ε-caprolactone-co-αClεCL) is a convenient way to access to amphiphilic and biocompatible copolymers.
