Time‐resolved luminescence anisotropy studies of the relaxation behaviour of polymers. 2. On the intramolecular mobility of poly(butyl methacrylate) in dilute solution

Abstract

Time-resolved anisotropy measurements (TRAMS) have been used to study the relaxation behaviour of poly(butyl methacrylate) (PBMA) in dilute solution both in toluene and dichloromethane. Various fluorescent labels (residues from copolymerisation of BMA with ca 0.3 mol% of acenaphthylene (ACE), 1-vinylnaphthalene (VN), 1-naphthylmethyl methacrylate, 9-phenyanthrylmethyl methacrylate, and 9-anthrylmethyl methacrylate (AMMA)) were used. It was found that, as expected, ACE and VN provided information on the segmental motion of PBMA. The fluorescence anisotropies of the various ester labels reflected the influence of motion, independent of that of the PBMA backbone, upon the observed relaxation behaviour. The motion of AMMA, in particular, could be resolved, with confidence, into components corresponding to segmental relaxation of both the polymer and ester group motion. Clearly, in this system, motion of the labelled ester is not fully cooperative with that of the polymer backbone, even at the high test frequencies to which these fluorescence measurements correspond.

Synthesis and Optical Properties of all‐trans‐Oligodiacetylenes

“…[70] This technique can provide information regarding the transition dipole moment and molecular geometry, and has proven to be useful in recent investigations of the conformational behavior of (water)-soluble polymers in solution. [71,72] Since all-trans ODAs are roughly rod-shaped in their most extended conformation, and possess a relatively large axial ratio, the rotation of the molecules around the longitudinal axis progresses evidently much faster than the rotations around the two short, perpendicular axes, which are not expected to differ significantly from each other. In line with this, the observed anisotropy decay kinetics r(t) of ODAs are mono-exponential, characterized by an initial anisotropy value r 0 and one rotation correlation time (t R ): [69] fðtÞ ¼ r 0  expðÀt=t R Þ ð 2Þ…”