ma7b01401_si_001.pdf (2.53 MB)
Effect of Spacer Stiffness on the Properties of Hyperbranched Polymers
journal contribution
posted on 2017-10-18, 19:09 authored by Suresh
Kumar Perala, S. RamakrishnanA series
of peripherally clickable hyperbranched polyesters were
prepared wherein the stiffness of the spacer segment between branching
junctions was systematically varied. Three different four-carbon spacers
were studied: one was fully saturated (HBPC4-S), another bears a double
bond (HBPC4-DBc), and a third carries a triple bond
(HBPC4-TB); in the case of the sample with a double bond c indicates cis-rich isomer. The glass transition
temperatures of the HB polyesters were seen to increase with the stiffness
of the spacer segment from 27 to 60 °C. Furthermore, when the
peripheral propargyl groups of the HB polyesters were quantitatively
clicked with a crystallizable docosyl (C-22) azide, all the derivatives
exhibited sharp melting/crystallization peaks in the DSC traces, indicative
of segregation and colocalization of the peripheral segments. WAXS
data confirmed the crystallization of the alkyl segments in a paraffinic
lattice, while SAXS profiles revealed the formation of a lamellar
morphology; the interlamellar spacing reflected the compactness of
the HB polymeric core and also the adaptability of the core toward
the self-segregation. Whereas the effect of such structural variations
in linear polyesters has been examined extensively, this represents
the first study that reveals the implications chain stiffness and
geometry on the properties of hyperbranched polymers.