Combining Modular Ligation and Supramolecular Self‐Assembly for the Construction of Star‐Shaped Macromolecules

A well‐defined random copolymer of styrene (S) and chloromethylstyrene (CMS) featuring lateral chlorine moieties with an alkyne terminal group is prepared (P(S‐co‐CMS), = 5500 Da, PDI = 1.13). The chloromethyl groups are converted into Hamilton wedge (HW) entities (P(S‐co‐HWS), = 6200 Da, PDI = 1.13). The P(S‐co‐HWS) polymer is subsequently ligated with tetrakis(4‐azidophenyl)methane to give HW‐functional star‐shaped macromolecules (P(S‐co‐HWS))₄, = 25 100 Da, PDI = 1.08). Supramolecular star‐shaped copolymers are then prepared via self‐assembly between the HW‐functionalized four‐arm star‐shaped macromolecules ( P(S‐co‐HW )) ₄ and cyanuric acid (CA) end‐functionalized PS (PS–CA, = 3700 Da, PDI = 1.04), CA end‐functionalized poly(methyl methacrylate) (PMMA–CA, = 8500 Da, PDI = 1.13) and CA end‐functionalized polyethylene glycol (PEG–CA, = 1700 Da, PDI = 1.05). The self‐assembly is monitored by ¹H NMR spectroscopy and light scattering analyses.     

Synthesis and self‐assembly morphologies of amphiphilic multiblock copolymers [poly(ethylene oxide)‐b‐polystyrene]n via trithiocarbonate‐embedded PEO macro‐RAFT agent

An amphiphilic multiblock copolymer [poly(ethylene oxide)‐b‐polystyrene]_n [(PEO‐b‐PS)_n] is synthesized by using trithiocarbonate‐embedded PEO as macro‐RAFT agent. PEO with four inserted trithiocarbonate (M_n = 9200 and M_w/M_n = 1.62) groups is prepared first by condensation of α, ω‐dihydroxyl poly(ethylene oxide) with S, S′‐Bis(α, α′‐dimethyl‐α″‐acetic acid)‐trithiocarbonate (BDATC) in the presence of pyridine, then a series of goal copolymers with different St units (varied from 25 to 218 per segment) are obtained by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The synthesis process is monitored by size exclusion chromatography (SEC), ¹H NMR and FT‐IR. The self‐assembled morphologies of the copolymers are strongly dependent of the length of PS block chains when the chain length of PEO is fixed, some new morphologies as large leaf‐like aggregates (LLAs), large octopus‐like aggregates (LOAs), and coarse‐grain like micelles (CGMs) are observed besides some familiar aggregates as large compound vesicles (LCVs), lamellae and rods, and the effect of water content on the morphologies is also discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6071–6082, 2006     

Well‐defined poly(oxazoline)‐b‐poly(acrylate) amphiphilic copolymers: From synthesis by polymer–polymer coupling to self‐organization in water

In this contribution, we report on the self‐assembly in water of original amphiphilic poly(2‐methyl‐2‐oxazoline)‐b‐poly(tert‐butyl acrylate) copolymers, synthesized by copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction. For such purpose, (poly(2‐methyl‐2‐oxazoline)) and (poly(tert‐butyl acrylate)) are first prepared by cationic ring‐opening polymerization and atom transfer radical polymerization, respectively. Well‐defined polymeric building blocks, ω‐N₃‐P(t‐BA) and α‐alkyne‐P(MOx), bearing reactive chain end groups, are accurately characterized by matrix‐assisted laser desorption ionization time‐of‐flight spectroscopy. Then, P(MOx)_n‐b‐P(t‐BA)_m are achieved by polymer–polymer coupling and are fully characterized by diffusion‐ordered NMR spectroscopy and size exclusion chromatography, demonstrating the obtaining of pure amphiphilic copolymers. Consequently, the latter lead to the formation in water of well‐defined monodisperse spherical micelles (R_H = 40–60 nm), which are studied by fluorescence spectroscopy, static light scattering, atomic force microscope, and transmission electronic microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of well‐defined azide‐terminated poly(vinyl alcohol) and their subsequent modification via click chemistry

A new azide‐functionalized xanthate, S‐(4‐azidomethylbenzyl) O‐(2‐methoxyethyl) xanthate, was synthesized and used to mediate the reversible addition fragmentation chain transfer polymerization of vinyl acetate. The polymerization was demonstrated to be controlled, and well‐defined PVAc with α‐azide, ω‐xanthate groups were obtained, the xanthate groups of which were further removed by radical‐induced reduction with lauroyl peroxide in the presence of excess 2‐propanol. Hydrolysis of α‐azide‐terminated PVAc (N₃‐PVAc) led to the formation of the corresponding α‐azide‐terminated PVA (N₃‐PVA). Finally, end‐modification of N₃‐PVA by click chemistry with alkyne‐end‐capped poly(caprolactone) (A‐PCL), alkynyl‐mannose, and alkynyl‐pyrene was carried out to obtain a new block copolymer PCL‐b‐PVA, and two PVA with mannose or pyrene as the end functional groups. The polymers were characterized by gel permeation chromatography, ¹H NMR spectroscopy, and FTIR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4494–4504, 2009     

Dendritic poly(benzyl ether)‐b‐poly(N‐vinylcaprolactam) block copolymers: Self‐organization in aqueous media,thermoresponsiveness and biocompatibility

Four generations of new amphiphilic thermoresponsive linear‐dendritic block copolymers (LDBCs) with a linear poly(N‐vinylcaprolactam) (PNVCL) block and a dendritic poly(benzyl ether) block are synthesized by atom transfer radical polymerization (ATRP) of N‐vinylcaprolactam (NVCL) using dendritic poly(benzyl ether) chlorides as initiators. The copolymers have been characterized by ¹H NMR, FTIR, and GPC showing controlled molecular weight and narrow molecular weight distribution (PDI ≤ 1.25). Their self‐organization in aqueous media and thermoresponsive property are highly dependent on the generation of dendritic poly(benzyl ether) block. It is observed for the LDBCs that the self‐assembled morphology changes from irregularly spherical micelles, vesicles, rod‐like large compound vesicles (LCVs), to the coexistence of spherical micelles and rod‐like LCVs, as the generation of the dendritic poly(benzyl ether) increases. The results of a cytotoxicity study using an MTT assay method with L929 cells show that the LDBCs are biocompatible. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 300–308     

Solid state self‐assembly of the single‐walled carbon nanotubes and poly(γ‐benzyl‐l‐glutamate)s with different conformations

A series of pyrenyl‐terminated poly(γ‐benzyl‐l ‐glutamate)s (py‐PBLGs) with controlled polymer molecular weight (M_W = 2.3–14.8 kg mol^?1) and molecular weight distribution (PDI = 1.17–1.55) have been prepared from 1‐pyrenemethylamine hydrochloride‐mediated ring‐opening polymerization (ROP) of γ‐benzyl‐l ‐glutamic acid based N‐carboxyanhydride (BLG‐NCA). FTIR analysis revealed that the py‐PBLG₉ was conformationally heterogeneous with 35.0% α‐helix, 55.6% β‐sheet, and 9.4% random coil conformations in the solid state, whereas the py‐PBLG₆₆ adopts 100% α‐helix conformation. Py‐PBLGs promote the dispersion of SWCNTs in organic solvents and in the PBLG solid through π–π interaction, as evidenced by the Raman spectroscopic studies. WAXD analysis revealed that the SWCNTs significantly affect the ordering of the py‐PBLG self‐assembly: the long range hexagonal packing of py‐PBLG₆₆ rods is notably enhanced by the addition of SWCNTs, whereas the lamellar packing of py‐PGLG₉ β‐sheets is weakened. In the hexagonal lattice, the SWCNTs are intercalated parallel to the py‐PBLG₆₆ rods, in contrast to the normal orientation of the SWCNTs with respect to the extended py‐PBLG₉ chains in the β‐sheets. The relative packing structure also affects the intermolecular interaction among the PBLGs: SWCNTs promote the interaction among the py‐PBLG₉ chains packed in a lamellar structure and weaken the intermolecular interaction among the py‐PBLG₆₆ columnar hexagonal array. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4489–4497     

Control of thermoresponsive property of urea end‐functionalized poly(N‐isopropylacrylamide) based on the hydrogen bond‐assisted self‐assembly in water

The precise synthesis and variation in the thermoresponsive property based on the supramolecular assembly of a novel urea end‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) were studied. A series of PNIPAMs with different diphenylurea groups at the chain end (X? Ph? NH? CO? NH? Ph? trz? PNIPAM: X = H, OCH₃, CH₃, NO₂, Cl, and CF₃) were synthesized by using a combination of the atom transfer radical polymerization and the copper(I)‐catalyzed azide‐alkyne cycloaddition. The cloud point of the obtained polymers depended on the hydrogen‐bonding ability of the introduced urea group. The ¹H NMR measurement suggested that the obtained PNIPAM assembled in water via the intermolecular hydrogen bonding by the terminal urea group. From the dynamic light scattering and transmission electron microscopy measurements, the aggregated nanoparticles of the resulting polymer were directly observed in water at a temperature below its cloud point. The hydrogen‐bonding property of the chain end urea group was concluded to be involved in the aggregation of the PNIPAM in water, leading to the variation in its cloud point. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6259–6268, 2009     

Synthesis and hierarchical superstructures of side‐chain liquid crystal polyacetylenes containing galactopyranoside end‐groups

Three kinds of chiral saccharide‐containing liquid crystalline (LC) acetylenic monomers were prepared by click reaction between 2‐azidoethyl‐2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranoside and 1‐biphenylacetylene 4‐alkynyloxybenzoate. The obtained monomers were polymerized by WCl₆‐Ph₄Sn to form three side‐chain LC polyacetylenes containing 1‐[2‐(2,3,4,6‐tetraacetyl‐β‐D ‐galactopyranos‐1‐yl)‐ethyl]‐1H‐[1,2,3]‐triazol‐4′‐biphenyl 4‐alkynyloxybenzoate side groups. All monomers and polymers show a chiral smectic A phase. Self‐assembled hiearchical superstructures of the chiral saccharide‐containing LCs and LCPs in solution state were studied by field‐emission scanning electron microscopy. Because of the LC behavior, the LC molecules exhibit a high segregation strength for phase separation in dilute solution (THF/H₂O = 1:9 v/v). The self‐assembled morphology of LC monomers was dependent upon the alkynyloxy chain length. Increasing the alkynyloxy chain length caused the self‐assembled morphology to change from a platelet‐like texture ( LC‐6 ) to helical twists morphology ( LC‐11 and LC‐12 ). Furthermore, the helical twist morphological structure can be aligned on the polyimide rubbed glass substrate to form two‐dimensional ordered helical patterns. In contrast to LC monomers, the LCP‐11 self‐assembled into much more complicate morphologies, including nanospheres and helical nanofibers. These nanofibers are evolved from the helical cables ornamented with entwining nanofibers upon natural evaporation of the solution in a mixture with a THF/methanol ratio of 3:7. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6596–6611, 2009     

Phosphine‐free direct arylation synthesis and self‐assembled nanostructure analysis of poly(3‐hexylselenophene)

Poly(3‐hexylselenophene)s (P3Hs) with high regioregularity (RR = 92–96%), that is, regioregular poly(3‐hexylselenophene)s (rr‐P3HSs), have been synthesized under the phosphine‐free direct arylation conditions in the presence of PdCl₂ as a precatalyst. rr‐P3HS with the high molecular weight (M_n ～ 10,000) was obtained as a result of screening of direct arylation conditions. Subsequently, the influences of primary structure, molecular weight (M_n = 3900–10,000) and regioregularity (RR = 57–96%), on optical properties and self‐assembled nanostructure of P3HS were investigated. X‐ray diffraction demonstrated that molecular weight, regioregularity, and preparation method of films dominate the crystallization behavior of P3HS. Among these parameters, it was evident that a high degree of regioregularity was the most fundamental contributor to achieve pure crystalline nanostructure. Furthermore, nanoassembly based on pure crystalline nanostructure, such as non‐woven fibrous and bundle‐like spherulitic self‐assembled nanostructures, was successfully prepared in rr‐P3HS, respectively, by appropriate modulation of the aforementioned parameters. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2749–2755     

Synthesis and self‐assembly of helical polypeptide‐random coil amphiphilic diblock copolymer

Three amphiphilic rod‐coil diblock copolymers, poly(2‐ethyl‐2‐oxazoline‐b‐γ‐benzyl‐L ‐glutamate) (PEOz‐b‐PBLG), incorporating the same‐length PEOz block length and various lengths of their PBLG blocks, were synthesized through a combining of living cationic and N‐carboxyanhydride (NCA) ring‐opening polymerizations. In the bulk, these block copolymers display thermotropic liquid crystalline behavior. The self‐assembled aggregates that formed from these diblock copolymers in aqueous solution exhibited morphologies that differed from those obtained in α‐helicogenic solvents, that is, solvents in which the PBLG blocks adopt rigid α‐helix conformations. In aqueous solution, the block copolymers self‐assembled into spherical micelles and vesicular aggregates because of their amphiphilic structures. In helicogenic solvents (in this case, toluene and benzyl alcohol), the PEOz‐b‐PBLG copolymers exhibited rod‐coil chain properties, which result in a diverse array of aggregate morphologies (spheres, vesicles, ribbons, and tube nanostructures) and thermoreversible gelation behavior. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3108–3119, 2008     

Atom transfer radical polymerization of methyl methacrylate via reversibly supported catalysts on silica gel via self‐assembly

A reversible catalyst immobilization system via self‐assembly of hydrogen bonding between thymine anchored on silica gel support and 2,6‐diaminopyridine functionalized with a catalyst (copper bromide‐N,N,N′,N′‐tetraethyldiethylenetriamine (TEDETA) complex) was developed for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). At elevated temperatures, the hydrogen bonding disassociated and released the catalyst as free small molecules for catalysis, which effectively mediated a living polymerization of MMA, producing PMMA with controlled molecular weight and narrow molecular weight distribution (<1.3). At room temperature, the catalyst assembled on the silica gel support by hydrogen bonding, and thus could be recovered and reused for a second run of ATRP. The recovered catalyst still mediated a living polymerization of MMA with reduced activity (54–64%), but had much improved control of the polymerization. The resulting PMMA had molecular weights very close to theoretical vales. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 22–30, 2004     

Hydrogen‐bonded supramolecular polymers from derivatives of α‐amino‐ε‐caprolactam: A bio‐based material

Hydrogen‐bonded supramolecular polymers were prepared from the derivatives of α‐amino‐ε‐caprolactam (ACL), obtained from a renewable resource. Several self‐complimentary bis‐ or tetra‐caprolactam monomers were synthesized by varying the number of carbons of the spacer between the hydrogen‐bonding end groups. Physical properties of these hydrogen‐bonded polymers were clearly demonstrated by differential scanning colorimetry, solid‐state NMR, and X‐ray powder diffraction analyses. The supramolecular behavior was also supported by fiber formation from the melt for several of these compounds, and stable glassy materials were prepared from the physical mixtures of two different biscaprolactams. The self‐association ability of ACL was also used by incorporating ACL at the chain ends of low‐molecular weight Jeffamine (M_n = 900 g/mol) using urea and amide linkages. The transformation of this liquid oligomer at room temperature into a self‐standing, transparent film clearly showed the improvement in mechanical properties obtained by the introduction of terminal hydrogen‐bonding groups. Finally, the use of monomers with a functionality of four gave rise to network formation either alone or combination with bifunctional monomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A “plug and play” polymer through biocomplementary hydrogen bonding

This article describes a DNA‐like polymer that exhibits the ability to self‐assemble through hydrogen bonding. We synthesized poly[1‐(4‐vinylbenzyl)thymine] (PVBT) and 9‐hexadecyladenine (A‐C16) through an atom transfer radical polymerization (ATRP) and alkylation, respectively. Biocomplementary PVBT/A‐C16 hierarchical supramolecular complexes formed in dilute DMSO solution through nucleobase recognition, that is, hydrogen bonding interactions between the thymine (T) groups of PVBT and the adenine (A) group of A‐C16; evidence for this molecular recognition was also gained from dynamic light scattering studies. ¹H NMR titration studies in CDCl₃ showed that T–A complexes formed rapidly on the NMR time scale with high association constants (up to 534 M^?1). Moreover, FTIR spectroscopic, differential scanning calorimetry, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering analyses provided further details into the nature of the self‐assembly of these systems. In the bulk state, these complexes self‐assemble into well‐ordered lamellar structures; the changing d‐spacing distance (ranging from 4.98 to 2.32 nm) at different A‐C16 loadings reveals that the molecular structures of the PVBT/A‐C16 complexes are readily tailored. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6416–6424, 2008     

Well‐defined amphiphilic polymethylene‐b‐poly(acrylic acid) diblock copolymers: New synthetic strategy and their self‐assembly

Well‐defined amphiphilic polymethylene‐b‐poly (acrylicacid) diblock copolymers have been synthesized via a new strategy combining polyhomologation and atom transfer radical polymerization (ATRP). Hydroxyl‐terminated polymethylenes (PM‐OH) with different molecular weights and narrow molecular weight distribution are obtained through the polyhomologation of dimethylsulfoxonium methylides following quantitative oxidation via trimethylamine‐N‐oxide dihydrate. Subsequently, polymethylene‐based macroinitiators (PM‐MIs M_n = 1,300 g mol^?1 [M_w/M_n = 1.11] and M_n = 3,300 g mol^?1 [M_w/M_n = 1.04]) are synthesized by transformation of terminal hydroxyl group of PM‐OH to α‐haloester in ～100% conversion. ATRPs of tert‐butyl acrylate (t‐BuA) are then carried out using PM‐MIs as initiator to construct PM‐b‐P(t‐BuA) diblock copolymers with controllable molecular weight (M_n = 8,800–15,800 g mol^?1 M_w/M_n = 1.04–1.09) and different weight ratio of PM/P(t‐BuA) segment (1:1.7–1:11.2). The amphiphilic PM‐b‐PAA diblock copolymers are finally prepared by hydrolysis of PM‐b‐P(t‐BuA) copolymers and their self‐assembly behavior in water is preliminarily investigated via the determination of critical micelle concentrations, dynamic light scattering, and transmission electron microscope (TEM). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Spacer‐length‐dependent association in polymers with multiple‐hydrogen‐bonded end groups

Herein, we investigate the influence of spacer length on the homoassociation and heteroassociation of end‐functionalized hydrogen‐bonding polymers based on poly(n‐butyl acrylate). Two monofunctional ureido‐pyrimidinone (UPy) end‐functionalized polymers were prepared by atom transfer radical polymerization using self‐complementary UPy‐functional initiators that differ in the spacer length between the multiple‐hydrogen‐bonding group and the chain initiation site. The self‐complementary binding strength (K_dim) of these end‐functionalized polymers was shown to depend critically on the spacer length as evident from ¹H NMR and diffusion‐ordered spectroscopy. In addition, the heteroassociation strength of the end‐functionalized UPy polymers with end‐functionalized polymers containing the complementary 2,7‐diamido‐1,8‐naphthyridine (NaPy) hydrogen‐bond motif is also affected when the aliphatic spacer length is too short. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

New tethered ansa‐bridged zirconium catalysts: Insights into the “self‐immobilization” mechanism

New ω‐alkenyl‐substituted ansa‐bridged bisindenyl zirconium complexes are prepared and tested as self‐immobilized catalysts for ethene polymerization. But, even at very high concentration of the tethered complexes and low pressure of ethene, there is no evidence of their insertion into the polyethene chain. A “cross polymerization” test, performed by copolymerizing the tethered complexes with ethene using rac‐Me₂Si(2‐MeBenzInd)₂ZrCl₂ ( MBI ), does not lead to their incorporation into the polyethene chain. However, the corresponding ligand proves to be a suitable comonomer for ethene, and, through copolymerization promoted by MBI, innovative poly(ethene‐co‐2,2′‐bis[(1H‐inden‐3′‐yl)‐hex‐5‐ene) copolymers are prepared and characterized by ¹³C NMR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis,conformation transition,liquid crystal phase,and self‐assembled morphology of thermosensitive homopolypeptide

Thermosensitive diethylene glycol‐derived poly(L ‐glutamate) homopolypeptides (i.e., poly‐L ‐EG₂‐Glu) with different molecular weights (MW) (M_n,GPC = 5380–32520) were synthesized via the ring‐opening polymerization (ROP) of EG₂‐L ‐glutamate N‐carboxyanhydride (EG₂‐Glu‐NCA) in N,N‐dimethylformamide solution at 50 °C. Their molecular structure, conformation transition, liquid crystal (LC) phase behavior, lower critical solution temperature (LCST) transition, and morphology evolution were thoroughly characterized by means of FTIR, ¹H NMR, gel permeation chromatography, differential scanning calorimetry, wide angle X‐ray diffraction, polarized optical microscope, transmission electron microscope, and dynamic light scattering. In solid state, the homopolypeptide poly‐L ‐EG₂‐Glu presented a conformation transition from α‐helix to β‐sheet with increasing their MW at room temperature, while it mainly assumed an α‐helix of 80–86% in aqueous solution. Poly‐L ‐EG₂‐Glu showed a thermotropic LC phase with a transition temperature of about 100 °C in solid state, while it gave a reversible LCST transition of 34–36 °C in aqueous solution. The amphiphilic homopolypeptide poly‐L ‐EG₂‐Glu self‐assembled into nanostructures in aqueous solution, and their critical aggregation concentrations decreased with increasing MW. Interestingly, their morphology changed from spherical micelles to worm‐like micelles, then to fiber micelles with increasing MW. This work provides a simple method for the generation of different nanostructures from a thermosensitive biodegradable homopolypeptide. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of azobenzene‐containing polymers via RAFT polymerization and investigation on intense fluorescence from aggregates of azobenzene‐containing amphiphilic diblock copolymers

The well‐defined azobenzene‐containing homopolymers, poly{6‐(4‐phenylazophenoxy)hexyl methacrylate (AHMA)} (PAHMA), were synthesized via reversible addition fragmentation chain transfer polymerization (RAFT) in anisole solution using 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as the RAFT agent and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The first‐order kinetic plot of the polymerization and the linear dependence of molecular weights of the homopolymers with the relatively low polydispersity index values (PDIs ≤ 1.25) on the monomer conversions were observed. Furthermore, the amphiphilic diblock copolymer, poly{6‐(4‐phenylazophenoxy)hexyl methacrylate (AHMA)}‐b‐poly{2‐(dimethylamino)ethyl methacrylate (DMAEMA)} (PAHMA‐b‐PDMAEMA), was prepared with the obtained PAHMA as the macro‐RAFT agent. The structures and properties of the polymers were characterized by ¹H NMR and GPC, respectively. Interestingly, the amphiphilic diblock copolymers in chloroform (CHCl₃) solution (PAHMA₂₃‐b‐PDMAEMA₉₇ (4 × 10^?5 M, M_n(GPC) = 18,400 g/mol, PDI = 1.48) and PAHMA₂₈‐b‐PDMAEMA₁₁₇ (6 × 10^?5 M, M_n(GPC) = 19,300 g/mol, PDI = 1.51) exhibited the intense fluorescence emission at ambient temperature. Moreover, the fluorescent intensity of PAHMA‐b‐PDMAEMA in CHCl₃ was sensitive to the ultraviolet irradiation at 365 nm, which increased within the first 10 min and later decreased when irradiation time was prolonged to 30 min or longer. The well distributed, self‐assembled micelles composed of azobenzene‐containing amphiphilic diblock copolymers, (PAHMA‐b‐QPDMAEMA)s (QPDMAEMA is quaternized PDMAEMA), in the mixed N,N‐dimethyl formamide (DMF)/H₂O solutions were prepared. Their fluorescent intensities decreased with the increasing amount of water. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5652–5662, 2008     

Chiral self‐discrimination of the enantiomers of α‐phenylethylamine derivatives in proton NMR

Two types of chiral analytes, the urea and amide derivatives of α‐phenylethylamine, were prepared. The effect of inter‐molecular hydrogen‐bonding interaction on self‐discrimination of the enantiomers of analytes has been investigated using high‐resolution ¹H NMR. It was found that the urea derivatives with double‐hydrogen‐bonding interaction exhibit not only the stronger hydrogen‐bonding interaction but also better self‐recognition abilities than the amide derivatives (except for one bearing two NO₂ groups). The present results suggest that double‐hydrogen‐bonding interaction promotes the self‐discrimination ability of the chiral compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

Hydrogen‐bonding‐aided synthesis of novel ladderlike organobridged polysiloxane containing side‐chain naphthyl groups

With a hydrogen‐bonding template, a novel soluble aryl amide‐bridged ladderlike polysiloxane, containing naphthyl as the side‐chain group, has been successfully synthesized via a stepwise coupling polymerization. It is proposed that the monomer, N,N′‐di(3‐naphthyldiethoxylsilyl‐propyl)‐[4,4′‐oxybis(benzyl amide)], prepared by Grignard and hydrosilylation reactions, undergoes self‐assembly first via amido hydrogen bonding and then via hydrolysis, followed by condensation under controlled reaction conditions to yield a high molecular weight, soluble, dark yellow polymer. The analytical results (Fourier transform infrared, ¹H NMR, ²⁹Si NMR, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry) show that the polymer possesses an ordered ladderlike architecture. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 636–644, 2003