Amphiphilic random and random block terpolymers with PEG, octadecyl, and oleyl pendants for controlled crystallization and microphase separation

Abstract

Amphiphilic random and random block terpolymers bearing PEG chains, crystalline octadecyl groups, and amorphous oleyl groups were designed to control crystallization and microphase separation in the solid state.

Water-Assisted Microphase Separation of Cationic Random Copolymers into Sub-5 nm Lamellar Materials and Thin Films

“…The random copolymers bearing hydrophobic groups longer than octyl groups formed lamellar structures; the critical carbon number of the hydrophobic pendants to the lamellar structures was 8. In contrast to PEG-bearing random copolymers, cationic random copolymers bearing amorphous hydrophobic groups also afforded microphase separation at room temperature and gave transparent or translucent polymer materials with sub-5 nm lamellar structures. The glass transition temperature of those cationic random copolymers was tunable by the hydrophobic pendants and composition.…”

“…To construct self-assembled structures precisely in the size range between 10 and a few nm, sub-10 nm microphase separation systems with (co)­polymers have been developed typically via the two strategies. One is microphase separation of high χ–low N linear block copolymers, where χ is the Flory–Huggins interaction parameter and N is the degree of polymerization. − The other is the self-assembly of polymer side or graft chains: microphase separation of (1) homopolymers between their main chains and side chains, − (2) random or alternating copolymers between their different side chains, − and (3) brush polymers between their different side chains in the same monomers. − The former requires precision synthesis of well-defined block copolymers with narrow molecular weight distribution via living polymerization to control the domain spacing in microphase separation. In contrast, the latter often affords to control the domain spacing precisely by the length of the side chains and the copolymer composition and thereby use common (co)­polymers for the construction of well-defined nanostructures.…”

“…In contrast, the latter often affords to control the domain spacing precisely by the length of the side chains and the copolymer composition and thereby use common (co)­polymers for the construction of well-defined nanostructures. For example, amphiphilic random copolymers bearing hydrophilic poly­(ethylene glycol) (PEG) or hydroxyethyl groups and hydrophobic crystalline octadecyl groups induce microphase separation of their side chains via the crystallization of the octadecyl groups to form sub-10 nm lamellar structures in the solid state (Figure b). ,,− The domain spacing was controlled between 3 and 6 nm by tuning the copolymer composition and the length of hydrophilic PEG side chains . However, such PEG-based random copolymers required crystalline octadecyl groups (−C 18 H 37 ) for the formation of lamellar structure via pendant microphase separation; i.e., the combination of PEG and amorphous hydrophobic pendants did not lead to such well-defined lamellar structures in the bulk state …”

Multilayered Lamellar Materials and Thin Films by Instant Self-Assembly of Amphiphilic Random Copolymers

“…Controlled self-assembly of (co)­polymers and related compounds is a key technology to construct ordered nanostructures and nanopatterns in functional materials, thin films, and devices for various applications (e.g., bioapplications, membranes, electronic devises, and lithography). − Among them, controlling sub-10 nm scale structures is often required to realize targeted properties and performance, while easy access to such small nanostructures is still challenging in self-assembly of polymers. For this purpose, two types of strategies have typically been examined: One is self-assembly of high-χ low- N block copolymers comprising short and incompatible chains (χ, Flory–Huggins interaction parameter; N , the total degree of polymerization) − and the other is that of (co)­polymers bearing short and incompatible side chains, including brush, graft, random, copolymers, and homopolymers. − The former method involves well-controlled block copolymers with narrow molecular weight distribution, because N and molecular weight distribution directly affect the domain spacing and the uniformness . However, the latter possibly affords the control of the domain size and structures by the side chain length and composition, and thus, N and molecular weight distribution may not affect the domain spacing.…”

“…Typically, random copolymers bearing octadecyl groups and hydrophilic poly­(ethylene glycol) [PEG: −(OCH 2 CH 2 ) 9 OCH 3 ] pendants − induce microphase separation of the pendants to form sub-10 nm lamellar structures in the solid state. Owing to crystallization-driven self-assembly, the nanostructures are created just by solvent evaporation from the polymer solutions. − Thus, we anticipated that, if hydrophilic and small hydroxy groups and crystalline octadecyl groups were introduced as their pendants, resulting random copolymers would not only precisely form sub-5 nm lamellar structures via pendant self-assembly in the solid state, but also autonomously form multilayered lamellar structures on silicon substates by simple spin-coating, where the lamellar orientation and sequence would also be regulated by the preferential affinity of their side chains to the substrate surface and air interface.…”