Synthesis of star-shapee poly(epsilon-caprolactone)-b-poly(DL-lactic acid-alt-glycolic acid) with multifunctional initiator and stannous octoate catalyst
Cm. Dong et al., Synthesis of star-shapee poly(epsilon-caprolactone)-b-poly(DL-lactic acid-alt-glycolic acid) with multifunctional initiator and stannous octoate catalyst, MACROMOLEC, 34(14), 2001, pp. 4691-4696
Two types of three-arm or four-arm star-shaped hydroxy-terminated poly(epsi
lon -caprolactone) (PCL) were successfully synthesized via the ring-opening
polymerization of epsilon -caprolactone (CL) with multifunctional initiato
r, such as trimethylolpropane (TMP) or pentaerythritol (PTOL), and stannous
octoate (SnOct(2)) catalyst in bulk at 110 degreesC. The number-average mo
lecular weight of PCL is proportional to the molar ratio of monomer to init
iator. H-1 NMR spectroscopy of the resulting PCL indicates that it contains
a primary hydroxy end group in each arm. The star-shaped PCL with hydroxy
end groups can be used as a macroinitiator for block copolymerization with
DL-3-methylglycolide (MG) using SnOct(2) catalyst in bulk at 115 degreesC.
H-1 NMR spectra of the resulting block copolymers show that the molecular w
eights and the unit compositions of the block copolymers were controlled by
the molar ratios of MC monomer to hydroxy groups of PCL and MG to CL in fe
ed, respectively. Moreover, the molecular weights of the resulting block co
polymers linearly increased with the increase of the molar ratios of MG to
CL in feed. The molecular weight distributions of the block copolymers were
rather narrow (M-w/M-n = 1.09-1.26). C-13 NMR spectra of the resulting blo
ck copolymers clearly show their diblock structures, that is, PCL as the fi
rst block and poly(DL-lactic acid-ail-glycolic acid) (DL-PLGA50) with alter
nating structures of lactyl and glycolyl units as the second block. Therefo
re, two types of three-arm or four-arm star-shaped diblock copolyesters com
prising the first block PCL and the second block DL-PLGA50 were successfull
y synthesized via the sequential ring-opening polymerization of CL with mul
tifunctional initiator and SnOct(2) catalyst and then followed by copolymer
ization with MG.