Small‐angle X‐ray scattering study on concentration dependence of polymer chain dimension

Abstract

The concentration dependence of polymer chain dimensions was studied by a new type of "tagged polymer method in small-angle X-ray scattering. A small fraction of partially iodinated polystyrene, the tagged polymer, was mixed with polystyrene in toluene. From the excess scattering originated from the iodine, the radius of gyration of the polystyrene chain (M,= 110000) was estimated at various concentrations. It was found that the chain dimension decreases first rapidly and then decreases gradually with increasing polymer concentration, and that, in the bulk, it coincides with the unperturbed chain dimension. The result was compared with theoretical predictions. The theories applicable to low concentrations could predict well the chain dimension uptomassconcentrations ofca. 0,l g/cm3, while the theoriesapplicable to higher concentrations could not predict well the chain dimension at high concentrations. The conformation of the polymer chain was also discussed. More compact conformations than a random coil as well as the bundle model were not supported by the results. *I Vollmrrt et al. proposed this model from studies on polymer-polymer reaction, whereas,Worsfold'8', using the analogous method, has claimed that the procedure of Vollmert was inadequate, and that the polymer chains are freely interpenetrating. Recently, Vollmert himself' 9 , has modified his model based on further experiments.

Fluorescence and aggregation behavior of a polyimide in solutions

“…It is an interesting phenomenon, which suggests that the decrease of coil size is very pronounced during the initial stage of shrinkage. This result agrees well with a similar observation by Qian et al 20) in their fluorescence study of polystyrene and is also in accordance with the small-angle neutron scattering 21) and small-angle X-ray scattering 22) results about the solution behavior of polystyrene.…”

Synthesis of polymer with defined fluorescent end groups via reversible addition fragmentation transfer polymerization for characterizing the conformations of polymer chains in solutions

“…Polymer chains are stretched in a good solvent in the dilute state due to the excluded volume effect . The chain dimension in a good solution decreases continuously when the concentration increases from the dilute state to the semidilute state, which is similar to those behaviors that have been well‐documented . However, in our system, a turning point was observed at 8.2 g/dL for PBMA 2w .…”

“…56 The chain dimension in a good solution decreases continuously when the concentration increases from the dilute state to the semidilute state, which is similar to those behaviors that have been welldocumented. 7,53,57 However, in our system, a turning point was observed at 8.2 g/dL for PBMA 2w . This value is comparable with the critical overlap concentration termed c*.…”

“…Scattering techniques, such as light scattering, X-ray scattering, and neutron scattering, are the most commonly used methods to characterize the size scale of single polymer chains. [5][6][7] However, light scattering can detect only the sizes of polymers with very large molecular weights due to the relatively large wavelength of light compared to the coil radius. 8 X-ray scattering has a more appropriate wavelength but sometimes encounters low contrast between the solvent and polymer.…”

Theory of tagged polymer method in small-angle X-ray scattering

“…Our interest is the special case that the tagged units are distributed randomly along the tagged molecule. The problem is to relate the averaged (11) …”