The luminescent hydroxyapatite nanorods co-doped with Eu 3+ and F − (named as FAp:Eu 3+ ) were synthesized through liquid-solid-solution strategy to control their size and morphology as well as improve their fluorescence. However, these luminescent FAp:Eu 3+ nanorods are hydrophobic nature and cannot be directly used for biomedical applications. In this work, we developed a novel strategy for surface modification of FAp:Eu 3+ nanorods with the combination of the surface ligand exchange reaction and photo-initiated reversible addition-fragmentation chain transfer (photo-RAFT) polymerization using the biocompatible and hydrophilic poly(ethylene glycol) methacrylate (PEGMA) as the monomer. We demonstrated that the photo-RAFT polymerization is a facile and efficient route to fabricate hydrophilic FAp:Eu 3+ -polyPEGMA composites based on a series of characterization techniques. The FAp:Eu 3+ -polyPEGMA composites still well maintained the morphology and luminescent properties. Furthermore, the resultant FAp:Eu 3+ -polyPEGMA composites showed low cytotoxicity and desirable cell uptake behavior. These features suggested that the FAp:Eu 3+ -polyPEGMA composites are of great potential for biological imaging applications. More importantly, the photo-RAFT polymerization should be promising for preparation of many other luminescent nanocomposites owing to their advantages of photo-RAFT polymerization such as low polymerization temperature, high efficiency, absence of metal catalysts and good monomer applicability. It is therefore, the photo-RAFT could be extended for fabrication of many other multifunctional fluorescent composites for different biomedical applications.
Yuting Li,Xiyu Wang,Ying Cao,Wenjing Niu,Qing Zheng,Xinhua Lu,Yuanli Cai
We describe self-coacervation and nanocrystal topochemical photo-RAFT polymerization of ionic phenylalanine acrylamide. The charged monomer molecules undergo self-coacervation through nanoclustering, liquid-liquid phase separation, and crystallization in crowded droplets in water at pH 7.0 at 25 °C, leading to ultrathin lamellar nanocrystal-containing droplets capable of well-controlled topochemical photo-RAFT polymerization. Reaction induces pathway-dependent self-assembly involving one-dimensional (non)covalent polymerization of monomer nanoclusters to fibril bundles. Furthermore, monomer molecules within crystal lattice undergo one-dimensional rearrangements guided by growing polymer segments, leading to the nanocrystal transition to perforated lamellar hollow sieves accompanied by decreased crystallinity, and the subsequent interfacial topochemical polymerization of monomer nanoclusters site-specifically along newly activated sites of sieve edges, leading to sieve-centred parallel-growing fibrils. Further reaction leads to densely-charged ultrathin fibril lamellae physically crosslinked by fibril network knots. Consequently, the well-controlled topochemical photo-RAFT polymerization up to >98% conversion was achieved shortly in 1 h, under ecofriendly ambient aqueous conditions. This work provides a robust platform of topochemical photo-RAFT polymerization that proceeds with unprecedentedly high molecular weight controllability.
Xuejun Chen,Na Xu,Nan Li,Lican Lu,Yuanli Cai,Ying Zhao,Dujin Wang
We describe the programmable selectivity of intra-/inter-chain coordination in the subcomponent self-assembly of a primary amine based block copolymer. A well-defined poly(6-aminohexylmethacrylamide hydrochloride)-block-poly(N-2-hydroxypropylmethacrylamide) (PHPMA-b-PAHMA) was synthesized via visible light activated aqueous RAFT polymerisation at 25 °C. The conjugation of 2-hydroxy-5-methoxybenzaldehyde (HMBA) in the absence or presence of small fractions of the nickel ion complex was monitored using 1H NMR and UV spectroscopy. Subcomponent self-assembly and the programmable selectivity of intra-/inter-chain coordination were studied using dynamic light scattering and 1H NMR. The results demonstrated that the coordinated HMBA was much more reactive than the free HMBA, which promoted the collapse and hydrophobic association of polymer chains and thus brought about the autocatalysis of imine formation inside the collapsed “hot spots”. The polymer chains progressively assembled into narrowly-distributed nanoparticles on adding small fractions of NiII(HMBA)2 rather than autopoietically splitting into smaller ones, as observed on adding pure HMBA. More importantly, the diversity of subcomponent self-assembly and solubility of aggregates originated from the programmable selectivity of intra-/inter-chain coordination.
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