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

Abstract

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 (oDMS) and lactic acid (oLA) were synthesized, each having either a discrete number of repeat units or a variable block length. Ligation of the blocks resulted in oDMS–oLA 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 oDMS–oLA, 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.

Linking two worlds in polymer chemistry: The influence of block uniformity and dispersity in amphiphilic block copolypeptoids on their self‐assembly

“…It seems that uniformity of the blocks is more likely to create sharp interfaces, whereas disperse blocks can more readily create curved interfaces. These results are in accordance to the findings of Meijer and coworkers who showed that an increase of dispersity resulted in the widening of the space domain and a decrease of the overall degree of ordering.…”

“…It was shown, that the phase separation of amphiphilic block co‐oligomers is sensitive to an increase of dispersity. Increasing the dispersity of blocks resulted in a widening of the domain spacing, increase of the stability of the microphase‐segregated state, and a decrease of the overall ordering . Additional investigations displayed the influence of the dispersity toward the self‐assembly of ABA‐type amphiphilic block co‐oligomers in aqueous solution .…”

“…It was only recently, that Meijer and coworkers published first investigations showing the importance of the difference between uniform and disperse block copolymers with respect to their microphase separation . These were the first studies that directly compared chemically identical block co‐oligomers that only differed in their dispersity.…”

Microphase separation of highly amphiphilic, low N polymers by photoinduced copper-mediated polymerization, achieving sub-2 nm domains at half-pitch

“…Our rationale was that PFOBiB would itself be a block (F13) with discrete dispersity, and possess a high χ interaction parameter with a polar homopolymer, which maintains a low N. PFOBiB was characterized by 1 H, 13 C and 19 F NMR spectroscopy ( Fig. S1-3 †), the excessive splitting observed in the 13 C spectrum is a result of carbon-fluorine coupling.…”

“…11 Dispersity (Đ) is a further important factor affecting bulk microphase separation, in which an increase in Đ has been shown to change morphology, increase domain spacing and decrease overall degree of order. [12][13][14] There have been several recent reports of sub-10 nm domain sizes. 4,[15][16][17][18] In order to push the lower size limit even further, SCFT suggests that the combination of a fluorinated block with a block comprising of highly polar repeat units could lead to domain spacings as small as 2 nm.…”