Microphase Separation Study of Amphiphilic ROMP Block Copolymers by SAXS and TEM

Abstract

The self-assembly of block copolymers to form well-ordered structures is of great interest for the design of hierarchical materials. In this contribution, the morphologies and properties of well-defined block copolymers with narrow molecular weight distributions prepared by ring-opening metathesis polymerization are studied. Two series of amphiphilic AB-block copolymers poly [(endo,exo[2.2.1]bicyclohept-5-ene-2,3-dicarboxylic acid dimethyl ester)-b-(endo,exo[2.2.1]bicyclohept-5-ene-2,3-dicarboxylic acid)] of different block ratios and lengths were investigated by thermal analysis, small-angle X-ray scattering, and transmission electron microscopy. As observed by thermal gravimetric analysis and FTIR spectroscopy, the free carboxylic acid functionalities lead to anhydride formation at higher temperatures so that direct observation of the melt morphologies is not possible. However, by drop-casting polymer solutions in THF, which is a nonselective solvent for this type of block copolymer, well-ordered films were prepared. A variety of structured morphologies of block copolymers with different compositions was obtained. Perfectly ordered lamellar phases can be observed for AB-block copolymers where both blocks are of equal size. For block copolymers with ratios that deviate from 1:1, morphologies like lamellae with different lamella size, hexagonal cylinders, and globules with liquidlike packing were found.

Water‐soluble polymers from acid‐functionalized norbornenes

“…In almost all cases, their water solubility is due to the chemical functionalities on the polymer backbone. We and others have previously reported water‐soluble polymers containing noncharged poly(ethylene oxide) (PEO) side chains, as well as positively charged and zwitterionic water‐soluble polymers, all of which were obtained by ring‐opening metathesis polymerization (ROMP) 5–11. Here, we complement these previous papers with this report on a well‐defined polymer obtained from ROMP, which bears two carboxylic acid groups per repeat unit.…”

“…Early attempts by Harrison and Feast19 to polymerize the norbornene dicarboxylic acid monomer (using ROMP with transition metal salts in aqueous media) led to broad polydispersities and yielded only low molecular weights. Later, other groups used the popular ruthenium‐based catalysis developed by Grubbs to obtain the desired poly( exo,exo ‐5‐norbornene‐2,3‐dicarboxylic acid) or one of its stereoisomers with reasonably narrow polydispersities and good molecular weight control 11, 20, 21. However, they were using protection–deprotection chemistry, which added further steps and thus cost to the polymer synthesis.…”

Synthesis of Miktoarm Branched Conjugated Copolymers by ROMPing In and Out

“…Trimmel and coworkers demonstrated that symmetrical diblock polynorbornenes derived from 3 and endo,exo - 4 cast from THF, a nonselective solvent, form lamellar nanostructures. 31 In our system, however, the grafting-from step is inefficient with endo,exo - 4 (SI, Figure S26), so we employed exo,exo - 4 . 32 It is well known that the crystallization of P3HT interferes with block copolymer self-assembly, resulting in nanofibrillar structures.…”

“…The d-spacing observed by SAXS (41 nm for P2-OH and 35 nm for P3-OH ) is consistent with AFM observations, and greater than the spacing for the diblock alone (29 nm). 31 …”

Perspectives in 1H, 14N and 81Br solid-state NMR studies of interfaces in materials textured by self-assembled amphiphiles

“…In this context, ROMP is a versatile method as it allows us to prepare a variety of amphiphilic block copolymers by choosing the functional groups, by varying the block size and by preparing di, tri, tetra-(and more) block copolymers [65]. Therefore these amphiphilic block copolymers possess self-assembly properties as shown recently [66,67]. They are also potential candidates for the texturation of hybrid organic-inorganic materials, and we have started to analyse their interaction with Al precursors.…”