Dispersity under Scrutiny: Phase Behavior Differences between Disperse and Discrete Low Molecular Weight Block Co-Oligomers

High Resolution Image Download MS PowerPoint Slide An experimental study is presented in which we compare the bulk phase behavior of discrete and (partially) disperse diblock co-oligomers (BCOs) with high χ–low N . To this end, oligomers of dimethylsiloxane ( o DMS) and lactic acid ( o LA) were synthesized, each having either a discrete number of repeat units or a variable block length. Ligation of the blocks resulted in o DMS– o LA BCOs with dispersities ranging from <1.00001 to 1.09, as revealed by mass spectroscopy and size exclusion chromatography. The phase behavior of all BCOs was investigated by differential scanning calorimetry and small-angle X-ray scattering. Compared to the well-organized lamellae formed by discrete o DMS– o LA, we observe that an increase in the dispersity of these BCOs results in (1) an increase of the stability of the microphase-segregated state, (2) a decrease of the overall degree of ordering, and (3) an increase of the domain spacing .