The number of arms per molecule, determined by multi-angle laser light scattering
(MALLS), varied in the range of 36–100 depending on the N-alkyl group of 25 and the
molecular weight of macromonomer. Block-arm and mikto-arm star polymers
consisting of poly(N-octyl-m-benzamide) and poly(N–H-m-benzamide) were also
synthesized by this method. It should be noted that the
1
H NMR spectra of the
mikto-arm star polymer in DMSO at 23
C showed a weak signal of the poly
(N-octyl-m-benzamide) moiety, but its intensity increased to the expected level on
heating (Fig. 5). This observation indicates that the poly(N-octyl-m-benzamide)
moiety, which is insoluble in DMSO, is packed in the star polymers at 23
C and
extended at higher temperatures. It seems intriguing that semirigid aromatic polyamide
arms in star polymers can dynamically change their molecular geometry in response to
thermal stimulation, as in the case of star polymers composed of flexible coil polymers.
Scheme 34 Synthesis of star-shaped aromatic polyamides by copolymerization of polyamide
macromonomer (plane) with MBAA in the presence of AIBN
Fig. 5
1
H NMR spectra of mikto-arm star polymer in DMSO-d 6 at (a) 23
C and (b) 120
C
218
Y. Ohta and T. Yokozawa