Light-driven swimming particles hold great potential in wide applications ranging from next-generation drug delivery to versatile microrobotic devices. It is desired that the self-propelled microparticles should swim not only autonomously but also directionally to achieve their goals in their potential applications. This paper presents the first example of fully organic colloidal particles of a spiropyran-terminated hyperbranched polymer that can be driven and meanwhile steered by a UV light source, swimming straight towards the UV source. The mean-square velocities of the photochromic suspension particles are about 20 μm s⁻¹, and increase to about 54 μm s⁻¹ with the addition of NaCl of 0.5%. The phototactic propulsion is supposed to be originated from the UV irradiation-induced interfacial tension gradient on the surface of the colloidal particles. This finding allows for the design of new microengines for next-generation drug delivery systems, microrobotic devices, and self-adaptive photocatalysts, etc.

Reduction of bare carbon dots (CDs) in aqueous NaBH₄ solution is a facile and effective approach to enhance their fluorescence without any surface coverage. CDs are treated with dilute aqueous NaBH₄ solutions, enhancing their quantum yields (QYs) successfully from 1.6 % to 16 % which is comparable to semiconductive QDs in aqueous environments. If pristine CDs are treated hydrothermally prior to reduction by NaBH₄, QYs reach 40.5 %. This value is among the highest QYs reported for bare CDs in the literature. The approach to enhance fluorescence through chemical reduction is generally applicable to other kinds of CDs synthesized by various methods. Alteration of the chemical structure of the CDs by NaBH₄-reduction is analyzed by ¹³C NMR, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, which demonstrate that the carbonyl group content is decreased after NaBH₄-reduction, whereas the number of sp³-type carbon defects is increased. The valence-band maxima (VBM) near the surface related to the surface energy bands of the CDs are estimated by XPS. VBM data show a semiconducting layer on the surface of the CDs, and the VBM of the CDs decrease with increasing NaBH₄-reduction time. The layered graphite structures in the cores of the CDs are clearly observed by transmission electron microscopy (TEM). CDs could perhaps be regarded as semiconductive surface defect layers formed by chemical erosion over conductive graphite cores. Chemical reduction by NaBH₄ changes the surface-energy bands of the CDs, thus, enhances their fluorescence. The fluorescence properties of aqueous NaBH₄-reduced CDs are also studied for possible biological applications.

Novel amphiphilic hyperbranched-upon-dendritic polymers with a dendritic polyester core, a linear poly(ε-caprolactone) (PCL) inner shell, and a hyperbranched polyglycerol outer shell have been prepared. The structures of the hyperbranched-upon-dendritic polymers were characterized by using NMR spectra. The critical aggregating concentrations (CACs) of those amphiphilic hyperbranched-upon-dendritic polymers were measured by using pyrene as the polarity probe. To study the encapsulation performances of those hyperbranched-upon-dendritic polymers as unimolecular hosts, inter-molecular encapsulation was carefully prevented by controlling the host concentrations below their CACs and by washing with good organic solvents. The study on encapsulation of two model guest molecules, pyrene and indomethacin, was performed. The amounts of encapsulated molecules were dependent mainly on the size of inner linear shells. About three pyrene molecules or five indomethacin molecules were encapsulated in hyperbranched-upon-dendritic polymers with average PCL repeating units of two but different hyperbranched polyglycerol outer shells, whereas about five pyrene molecules or about 12 indomethacin molecules were encapsulated in those with PCL repeating units of nine. The encapsulated molecules could be released in a controlled manner. Thus, the hyperbranched-upon-dendritic polymers could be used as unimolecular nanocarriers with controllable molecular encapsulation dosage for controlled release. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4013–4019, 2010

Production of polar hyperbranched polymers and encapsulation of small particles in the hyperbranched polymers is like “forming” pouches and then “filling” these pouches. Modification of the end-groups of the hyperbranched polymers with relative apolar groups is like “sealing” the pouches. In this article, we demonstrated that two methods depending on changed sequences, i.e., Form-Fill-Seal and Form-Seal-Fill methods resulted in different sized small particles with size-depended properties. By using these approaches, small metal nano-particles can be encapsulated inside polar microzones of dendritic-star polymers taking advantage of the difference in partition coefficients instead of strong interactions between the dendritic polymers and ions. We used the methodology to produce small silver particles encapsulated in hyperbranched polyglycidol (HPG). The HPG was synthesized via anionic ring-opening multibranching polymerization of glycidol. The “sealing” process was fulfilled by polymerization of ε-caprolactone initiated from the end groups of HPG. In the Form-Fill-Seal approach, Ag⁺ was filled inside HPG, and then was sealed before reduction to Ag; whereas the “pouch” of HPG was sealed at first, and then Ag⁺ was filled inside HPG by diffusion in the Form-Seal-Fill approach. Mainly nanometer-sized silver particles were formed by the Form-Fill-Seal approach, whereas silver clusters of several atoms were formed in the Form-Seal-Fill approach. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

In this work, novel star-hyperbranched block copolymers containing four polystyrene arms and hyperbranched polyglycidol at the end of each arm (sPS-b-HPG) have been synthesized. The polystyrene arms were prepared through atom transfer radical polymerization of styrene starting from a four-arm initiator. The hydroxyl-terminated PS star polymers served as precursors for the cationic ring-opening polymerization of glycidol using BF₃·OEt₂ as the catalyst. The chemical structures of these block copolymers were characterized by using ¹H and ¹³C NMR. DSC analysis indicated that the star-hyperbranched block copolymers exhibited two distinct glass transition temperatures corresponding to the linear PS and the HPG segments, respectively. The addition of LiClO₄ increased the T_g of HPG segments at low concentrations, however, decreased the T_g at high concentrations. The T_g of PS segments was not affected by the addition of salts at all. Furthermore, the interaction of sPS-b-HPG with LiBr was studied by using viscosity analysis based on the Jones–Dole equation. The star-like PS core strengthened the interaction of sPS-b-HPG with Li ions that could facile the inhomogeneous distribution of Li cations and anions in different phases, which is important in polymeric electrolytes for lithium chemical power sources. The ionic conductivity of one sPS-b-HPG/LiClO₄ electrolyte was measured to be higher than that of HPG/LiClO₄ electrolyte. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 949–958, 2009

Carbon nanotubes (CNTs) are used as templates to synthesize regioselective polymers from enzymatic polymerization of phenol in water. About 90% of total polymeric units in the obtained polymers are the highly thermally stable oxyphenylene units. The polymer-yields are dependent on the quantities of CNTs used. On the basis of MWNT-templated enzymatic polymerization of phenol, covalent attachment of polyphenol chains to the surface of MWNT by way of a linking molecule, hydroquinone, is achieved. This approach supplies a novel way for producing high-performance polymers and for functionalization of the surface of CNT. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1627–1635, 2009

We functionalize the focal group of hyperbranched poly(phenylene sulfide) (HPPS) with benzyl, phenyl, and naphthyl group, respectively. DSC analysis shows that T_g of HPPS is increased from 55 to 93°C by functionalization of the focal group with a conjugated naphthyl group. The fluorescence properties of the three core-functionalized HPPS' are studied under the comparison with the original HPPS. Functionalization by a non-conjugated benzyl group has no effects on the fluorescence properties of HPPS at all. Both the phenyl-cored and the naphthyl-cored HPPS' give rise to a new highly polarized fluorescent peak around 500 nm due to the formation of intermolecular excimers with encumbered molecular rotation. Differing from the often reported significant increase in core fluorescence due to the so-called “antenna effect,” the fluorescence of HPPS backbones is drastically enhanced after functionalization of the cores with naphthyl groups that is 10- to 18-fold higher than the original HPPS' depending on the molecular weights of HPPS'. The phenyl-cored HPPS does not show a notable increase in fluorescence intensities compared with the original HPPS. The clear comparison results are rationalized by the restriction of intramolecular rotations of the naphthyl cores against the HPPS periphery. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008