POSS end-linked peptide-functionalized poly(ɛ-caprolactone)s and their inclusion complexes with α-cyclodextrin

Influence of Chain Length on the Self-Assembly of Poly(ε-caprolactone)-Grafted Graphene Quantum Dots

The multifarious applications of graphene quantum dots (GQDs) necessitate surface modifications to enhance their solution processability. Herein, we report the synthesis and self-assembly of GQDs grafted with poly(ε-caprolactone) (PCL) of different degrees of polymerization (3, 7, 15, and 21) produced from ring-opening polymerization. Optical and morphological studies unveil the transformation of the assemblies from J-aggregates to H-aggregates, accompanied by an alteration in morphology from toroid to spheroid to rodlike structures with increasing chain length of PCL. Functionalized GQDs with lower chain lengths of PCL at higher concentration also assemble into liquid-crystalline phases as observed from birefringent textures, which are later correlated to the formation of columnar hexagonal (Col_h) mesophases. However, no such behavior is observed at higher chain lengths of PCL under identical conditions. Therefore, it is evident that the variation in the PCL chain length plays a crucial role in the self-assembly, which is primarily triggered by the van der Waals force between the polymer chains dictating the π stacking of GQDs, resulting in different self- aggregated behavior.

Supramolecular Interaction-Assisted Fluorescence and Tunable Stimuli-Responsiveness of l-Phenylalanine-Based Polymers

Supramolecular host-guest interactions between randomly methylated β-cyclodextrin (RM β-CD) and side-chain phenylalanine (Phe) and Phe-Phe dipeptide-based homopolymers have been employed for the amplification of fluorescence emission of otherwise weakly fluorescent amino acid Phe. The host-guest complex has been characterized by ¹H and ¹³C NMR spectroscopy, two-dimensional rotating-frame overhauser spectroscopy, Fourier-transform infrared spectroscopy, UV-visible spectroscopy, and fluorescence spectroscopy. To gain insights into the origin of fluorescence in homopolymers, density functional theory calculations were performed where phenyl moieties inside the less polar core of β-CD were observed to form a π-π coupled complex resulting in an enhanced emission. Furthermore, the complex-forming ability of Phe, the guest molecule, has been employed in tuning the cloud point temperature (T_CP) of statistical copolymers derived from side-chain Phe/Phe-Phe-based methacrylate monomers and N-isopropylacrylamide. By varying the co-monomer feed ratios in the statistical copolymer and hence the concentration of RM β-CD throughout the polymer chain, host-guest interaction-assisted broad tunability in T_CP of the supramolecular polymeric complex has been achieved.