Impact of Polylactide Fluorinated End-Group Lengths and Their Dynamics on Perfluorohexane Microcapsule Morphology

Abstract

We have synthesized polylactide (PLA) polymers containing five distinct lengths of fluorinated end-groups (from C 3 F 7 to C 13 F 27). The influence of fluorinated end-groups length and their dynamics in chlorinated solvents (chloroform and dichloromethane) was investigated as a function of the presence of perfluohexane (PFH) and related to the morphology of capsules of PFH obtained using these fluorinated polylactides. 19 F spin-spin relaxation time (T 2) measurements revealed a reduced mobility of the fluorinated units with dependency on fluorinated chain length in the order C 3 F 7 >C 8 F 17 >C 13 F 27. The presence of perfluorohexane (PFH) led to a further decrease on the segmental mobility, indicating the existence of fluorous interactions. The T 2 relaxation time of the CF 3 resonance of PLA-C 3 F 7 decreased from 540±50 ms in CDCl 3 to 81±15 ms after the addition of PFH. Due to these fluorous interactions, PLA polymers containing short fluorinated groups (C 3 F 7 and C 6 F 13) led to microcapsules with core-shell morphologies, whereas those formulated with long F-units (C 8 F 17 , C 11 F 23 and C 13 F 27) favored the formation of multinucleated capsules as observed by confocal microscopy.