Liangzhi Hong

Publications (8)13.36 Total impact

• Article: Chiral imprinting of diblock copolymer single-chain particles.

  Gabriel Njikang, Guojun Liu, Liangzhi Hong
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  ABSTRACT: This Article reports the molecular imprinting of polymer single-chain particles that have a radius ∼3.7 nm. For this, the template L-phenylalanine anilide or L-ΦAA and a diblock copolymer PtBA-b-P(CEMA-r-CA) were used. Here, PtBA denotes poly(tert-butyl acrylate), and P(CEMA-r-CA) denotes a random block consisting of cinnamoyloxyethyl methacrylate (CEMA) and carboxyl-bearing (CA) units. In CHCl(3)/cyclohexane (CHX) with 64 vol % of CHX or at f(CHX) = 64%, a block-selective solvent for PtBA, PtBA-b-P(CEMA-r-CA) formed spherical micelles. The core consisted of the insoluble P(CEMA-r-CA) block and L-ΦAA, which complexed with the CA groups. Pumping slowly this micellar solution into stirred CHCl(3)/(CHX) at f(CHX) = 64% triggered micelle dissociation into single-chain micelles, which comprised presumably a solubilized PtBA tail and a collapsed P(CEMA-r-CA)/L-ΦAA head. Because the solvent reservoir was under constant UV irradiation, the photo-cross-linkable units in the P(CEMA-r-CA) head cross-linked, and the single-chain micelles were converted into cross-linked single-chain micelles or tadpoles. Synchronizing the micelle addition and photoreaction rates allowed the preparation, from this protocol, of essentially pure tadpoles at high final polymer concentrations. Imprinted tadpoles were procured after L-ΦAA was extracted from the tadpole heads. Under optimized conditions, the produced imprinted tadpoles had exceptionally high binding capacity and high selectivity for L-ΦAA. In addition, the rates of L-ΦAA release from and rebinding by the particles were high.
  Langmuir 06/2011; 27(11):7176-84. · 4.19 Impact Factor
• Article: Water-dispersible superparamagnetic microspheres adorned with two types of surface chains.

  Zhihan Zhou, Guojun Liu, Liangzhi Hong
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  ABSTRACT: Water-dispersible superparamagnetic polymer/γ-Fe(2)O(3) composite microspheres adorned with two types of surface polymer chains are prepared and characterized. To prepare these spheres, we first synthesize uniform γ-Fe(2)O(3) nanoparticles that are covered by poly(2-cinnamoyloxyethyl methacrylate)-block-poly(acrylic acid) (PCEMA-b-PAA). These nanoparticles are then mixed with a PCEMA homopolymer in CHCl(3) to form an oil phase. The oil phase is dispersed into water under vigorous stirring with the help of two diblock copolymer surfactants, PGMA-b-PCEMA and PSGMA-b-PCEMA. Here PGMA and PSGMA denote poly(glyceryl monomethacrylate) and succinated PGMA, respectively. Solid microspheres with cores composed of PCEMA and PCEMA-b-PAA-covered γ-Fe(2)O(3) nanoparticles are obtained after CHCl(3) evaporation and PCEMA photo-cross-linking. Under certain conditions, the coronal PGMA and PSGMA chains become segregated, thus producing surface bumps, ridges, and valleys. The PSGMA chains preferentially cover the protruding regions. The PSGMA carboxyl groups are used to immobilize bovine serum albumin (BSA). The immobilized BSA retains its activity and binds with anti-BSA. These spheres should be useful in immunoassays.
  Biomacromolecules 02/2011; 12(3):813-23. · 5.48 Impact Factor
• Article: Miktoarm Star Copolymers from the Chemical Stitching of Associating Block Copolymers

  Hongjing Dou, Liangzhi Hong, Guojun Liu
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  ABSTRACT: A new method for the synthesis of miktoarm star copolymers is proposed. To demonstrate its viability, diblock copolymers, PA-b-PSCOOH, with a carboxyl-bearing short PSCOOH block, and triblock copolymers, PB-b-PNH2-b-PB, with an amino-bearing short PNH2 block, were synthesized and characterized. Here PA and PB denote poly(tert-butyl acrylate) and poly(methyl methacrylate), respectively. The carboxyl- and amino-bearing blocks of the copolymers associated with one another due to carboxylate and ammonium ion pairing in dichloromethane. The addition of a coupling agent caused the amino and carboxyl groups to amidize and resulted in the fusion of the associating chains, thus producing miktoarm copolymers μ-(PA)1(PB)2 and μ-(PA)2(PB)2. Factors affecting the relative and total yields of μ-(PA)1(PB)2 and μ-(PA)2(PB)2 formation were investigated.
  04/2010;
• Article: Viscometric Study of Poly(2-cinnamoyloxyethyl methacrylate)

  Liangzhi Hong, Guojun Liu
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  ABSTRACT: Six poly(2-cinnamoyloxyethyl methacrylate) (PCEMA) samples with low polydispersity indices were derived from precursors prepared by anionic polymerization. Their intrinsic viscosities were determined in tetrahydrofuran (THF) and chloroform at 25 °C and in p-xylene between 55 and 82 °C. The data were treated to yield the Mark−Houwink−Sakurada parameters K and a. The a values suggested that THF and chloroform were good solvents for PCEMA at room temperature. The intrinsic viscosity data obtained in p-xylene were also analyzed by the Burchard−Stockmayer−Fixman method. Both the a values and the results of data treatment by the Burchard−Stockmayer−Fixman method suggest that p-xylene was a theta solvent for PCEMA at 60 °C. Using the K value at the theta temperature, we determined for PCEMA a characteristic ratio of 12.6, which is the ratio between its mean-square end-to-end distance in a theta solvent and that of a random flight chain.
  03/2010;
• Article: Macrocycles from the Photochemical Coupling of Preassociated Terminal Blocks of Block Copolymers

  Jiwen Hu, Ronghua Zheng, Jian Wang, Liangzhi Hong, Guojun Liu
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  ABSTRACT: Cyclization of long polymer chains is difficult because polymer chain ends have a low probability to contact one another and intramolecular cyclization has to compete with interchain coupling. To minimize intermolecular coupling, macrocycles are prepared traditionally under high dilution conditions, which limit the amount of polymer obtainable per volume of solvent. Reported in this paper is a new methodology for synthesizing polymer macrocycles. Instead of using polymers with one pair of reactive groups at the ends of a polymer chain, we use a block copolymer, poly[(2-cinnamoyloxyethyl methacrylate)-ran-(2-trifluoroacetoxyethyl methacrylate)]-block-poly(solketal methacrylate)-block-poly(tert-butyl acrylate)-block-poly(solketal methacrylate)-block-poly[(2-cinnamoyloxyethyl methacrylate)-ran-(2-trifluoroacetoxyethyl methacrylate)] or P(CEMA-r-TFAEMA)-b-PSMA-b-PtBA-b-PSMA-b-P(CEMA-r-TFAEMA), with reactive P(CEMA-r-TFAEMA) end blocks to increase the efficiency of end coupling. In our method, a micellar solution is first prepared in a solvent selectively poor for the end CEMA units. This micellar solution is then slowly pumped into a solvent reservoir or reactor under constant stirring and irradiation. In the reactor, where the polymer concentration remains low throughout the preparation for its conversion into macrocycles, the micelles dissociate quickly into end-associated rings or unimolecular micelles, and the rings then get covalently linked photochemically. Since the TFAEMA units in the end blocks are soluble in the solvent used and probably segregate preferentially on the surface of the “balls” formed from the aggregation of the end CEMA units, they help deter the chemical coupling of different macrocycles. Using this methodology, we can prepare large macrocycles in high purity and at high concentrations.
  07/2009;
• Source

  Available from: Junfang Li

  Article: Folding of Long Multiblock Copolymer (PI-b-PS-b-PI)n Chains Prepared by the Self-Assembly Assisted Polypolymerization (SAAP) in Cyclohexane

  Liangzhi Hong, Fangming Zhu, Junfang Li, To Ngai, Zuowei Xie, Chi Wu
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  ABSTRACT: The formation of polymeric micelles made of A−B−A triblock chains in a solvent selectively poor for the middle B-block concentrate and exposes two active end groups so that short triblock chains can be effectively coupled together to form a long (A−B−A)n multiblock chain with a controllable block length and sequence. Using this method, we successfully prepared a (PI-b-PS-b-PI)30 multiblock copolymer, starting from a triblock PI-b-PS-b-PI copolymer (Mn = 4.8 × 104 g/mol). The coupling efficiency with and without the self-assembly was compared. The folding of such long multiblock chains (Mn = 1.4 × 106 g/mol) in a dilute solution (10-5 g/mL) was studied by a combination of static and dynamic laser light scattering. The results reveal that such long multiblock chains do not collapse into single-chain globule in a dilute solution even when the solution temperature is much lower than the ϑ temperature. Instead, each PS block collapses into a small globule stabilized by the two attached PI blocks on the chain backbone to form a string of coils and beads so that the multiblock chain becomes thicker with an extended conformation without interchain or intrachain association, which is completely different for the association of initial triblock PI-b-PS-b-PI chains in a selective solvent, i.e., the formation of polymeric micelles.
  02/2008;
• Source

  Available from: cuhk.edu.hk

  Article: Slow relaxation mode in mixtures of water and organic molecules: supramolecular structures or nanobubbles?

  Fan Jin, Jing Ye, Liangzhi Hong, Hiufung Lam, Chi Wu
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  ABSTRACT: Aqueous solutions of tetrahydrofuran, ethanol, urea, and alpha-cyclodextrin were studied by a combination of static and dynamic laser light scattering (LLS). In textbooks, these small organic molecules are soluble in water so that there should be no observable large structures or density fluctuation in either static or dynamic LLS. However, a slow mode has been consistently observed in these aqueous solutions in dynamic LLS. Such a slow mode was previously attributed to some large complexes or supramolecular structures formed between water and these small organic molecules. Our current study reveals that it is actually due to the existence of small bubbles ( approximately 100 nm in diameter) formed inside these solutions. Our direct evidence comes from the fact that it can be removed by repeated filtration and regenerated by air injection. Our results also indicate that the formation of such nanobubbles in small organic molecule aqueous solutions is a universal phenomenon. Such formed nanobubbles are rather stable. The measurement of isothermal compressibility confirms the existence of a low density microphase, presumably nanobubbles, in these aqueous solutions. Using a proposed structural model, that is, each bubble is stabilized by small organic molecules adsorbed at the gas/water interface, we have, for the first time, estimated the pressure inside these nanobubbles.
  The Journal of Physical Chemistry B 04/2007; 111(9):2255-61. · 3.70 Impact Factor
• Source

  Available from: Junfang Li

  Article: How Are Insoluble Blocks Interacted with and Packed Inside a Micelle Made of Block Copolymers in a Selective Solvent?

  Liangzhi Hong, Fan Jin, Junfang Li, Yijie Lu, Chi Wu
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  ABSTRACT: It is well-known that block copolymers can form large core-shell micelles in a selective solvent. The ultrafiltration of such polymeric micelles made of polystyrene (PS) and polyisoprene (PI) block copolymers in n-hexane through small pores (20 nm) is possible only when the flow-rate-dependent hydrodynamic force in the range 10 -15 to 10 -12 N (i.e., 1 fN-1 pN) is sufficiently strong to pull individual copolymer chains out of the core and disintegrate each micelle. Therefore, we are able to find how strong insoluble PS blocks in the core interact with each other from such a critical flow rate. Our results reveal that the micelle retention gradually decreases as the flow rate increases, different from a sharp first-order coil-to-stretch transition of a flexible linear homopolymer chain under the same elongation flow field. As expected, the interaction strength increases as the PS block becomes longer. Each flow-rate dependence of the micelle retention can be converted to a hydrodynamic force distribution f(F h). For PS-b-PI diblock copolymers, f(F h) has a single peak in the range 1-200 fN, whereas for PI-b-PS-b-PI triblock copolymers, there are two separated peaks in f(F h), respectively, in the ranges 3-20 and 30-500 fN, attributing to two kinds of packing of the PS blocks inside the core; namely, the packing of unentangled and entangled insoluble PS blocks.