Structure formation in nanophase-separated systems with lamellar morphology: Comb-like vs. linear precision polymers

Elucidating the influence of side chains on the self-assembly of semi-flexible mesogens

In the development of functional materials, side chains are traditionally incorporated into the primary chemical structure to induce liquid-crystalline behavior or to enhance solubility for improved processability. However, emerging evidence suggests that side chains play a far more complex role. This study presents a case of a double helical supramolecular structure formed by star-shaped mesogens in the absence of specific interactions. The molecular conformation is primarily dictated by the self-assembly of the side chains, introducing a new organizational paradigm for semiflexible low-molecular-weight mesogens.

Order-order transitions in poly(N-octadecyl acrylamide-co-hydroxyethyl acrylamide) statistical copolymer films

This study demonstrates that a simple statistical copolymer can form self-assembled lamellae, whose structures depend on both the comonomer composition and the annealing temperature. Statistical copolymers of octadecyl acrylamide and hydroxyethyl acrylamide [p(ODA/HEAm)] were prepared via free-radical copolymerization, and their thermal properties were studied by differential scanning calorimetry. Thin films of p(ODA/HEAm) were prepared via spin-coating, and their structures were analyzed using X-ray diffraction. It was found that copolymers with HEAm contents between 28 and 50% formed self-assembled lamellae upon annealing at a temperature ∼10 °C above the glass-transition temperature. The self-assembled form was found to possess a "side-chain-mixed" lamellar structure, in which the ODA and HEAm side chains are oriented perpendicular to the lamellar plane composed of the polymer main chain. Interestingly, a copolymer with a HEAm content between 36 and 50% transformed from the side-chain-mixed lamellar structure to generate a "side-chain-segregated" lamellar structure upon annealing at a significantly higher temperature (∼50 °C above T_g). In this structure, the ODA and HEAm side chains were found to be oriented in opposite directions but perpendicular to the lamellar plane. The packing of the side chains in the lamellar structures was studied using Fourier-transform infrared spectroscopy. It was concluded that the structures of the self-assembled lamellae are determined by the strain forces generated during self-assembly, and by the segregation forces existing between the comonomers.

Secondary Structures in Synthetic Poly(Amino Acids): Homo- and Copolymers of Poly(Aib), Poly(Glu), and Poly(Asp)

The secondary structure of poly(amino acids) is an excellent tool for controlling and understanding the functionality and properties of proteins. In this perspective article the secondary structures of the homopolymers of oligo- and poly-glutamic acid (Glu), aspartic acid (Asp), and α-aminoisobutyric acid (Aib) are discussed. Information on external and internal factors, such as the nature of side groups, interactions with solvents and interactions between chains is reviewed. A special focus is directed on the folding in hybrid-polymers consisting of oligo(amino acids) and synthetic polymers. Being part of the SFB TRR 102 "Polymers under multiple constraints: restricted and controlled molecular order and mobility" this overview is embedded into the cross section of protein fibrillation and supramolecular polymers. As polymer- and amino acid folding is an important step for the utilization and design of future biomolecules these principles guide to a deeper understanding of amyloid fibrillation.

Preparation of antistatic epoxy resin coatings based on double comb-like quaternary ammonium salt polymers

Two kinds of double comb-like quaternary ammonium salt polymers P(DPA-EPI) and P(DBA-EPI) with lower polarity were designed and synthesized using epichlorohydrin (EPI), di-n-propylamine (DPA) and di-n-butylamine (DBA) as raw materials. The transparent antistatic epoxy resin coatings were obtained using the two polymers as antistatic agents, respectively. Because P(DPA-EPI) and P(DBA-EPI) with good hygroscopic performance are easily dissolved in epoxy resin paints and are nearly linearly arranged in the epoxy resin paints, the obtained transparent antistatic epoxy resin coatings achieve good antistatic properties. The values of ρ_s of the coatings reach 5.13 × 10⁸ Ω sq⁻¹ and 2.69 × 10⁸ Ω sq⁻¹, respectively, with a lower addition amount of polymers of only 1.0 wt%. The two antistatic epoxy resin coatings also have good durability. Compared to the epoxy resin coating, with the introduction of P(DPA-EPI) and P(DBA-EPI), the thermal stability and adhesion of the antistatic epoxy resin coatings do not change obviously, but the Rockwell hardness values slightly reduce.

The antistatic epoxy resin coatings using double comb-like quaternary ammonium salt polymers as antistatic agents reach good antistatic property with lower addition amount because polymers can dissolve and nearly linearly arrange in the coatings.

Tuning layered superstructures in precision polymers

An approach to influence and control layered superstructures by varying the methylene sequence length between two consecutive functional groups in linear precision polymers containing 2,6-diaminopyridine (DAP) groups is presented. Layered superstructures with repeating units involving three monomeric units along the chain direction with very high coherence lengths upto 110 nm are observed in case of shorter alkyl segments, (16 and 18 [Formula: see text] units), while more conventional layer superstructures incorporating only one monomer are found for related polymers with 20 [Formula: see text] units per methylene sequence. A building block model explaining the unusually large periodicity of three monomeric units is proposed wherein layers containing crystalline or amorphous methylene sequences occur in different combinations. Occurrence of different layered structures depending on crystallization conditions, methylene sequence length as well as functional group type is explained by a competition of H-interactions between the DAP groups and the van der Waal forces between the hydrophobic methylene groups.