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Polymerization-induced self-assembly (PISA) has been established as an efficient method to fabricate polymeric vesicles. In most PISA cases, the formation of vesicles is solely driven by the solvop...

A new strategy combing quantitative reactions and reversible-covalent chemistry is proposed for sequential synthesis of a series of sequence-controlled polymers with different sequences. Using a Michael addition reaction between acrylate and thiol, an aminolysis reaction of five-membered cyclic dithiocarbonate and a thiol substitution reaction of bromomaleimide and thiol, AB-, AB'C- and AB'CD-sequenced molecules are synthesized via AB, AB'C and AB'CD sequential monomer additions, respectively. These three molecules all have furan-protected maleimido group at one end, and the other end of AB-, AB'C- and AB'CD-sequenced molecules is amine, thiol and anthracene groups, respectively. Due to the fact that the furan-protected maleimido group can be efficiently transformed to maleimide group at high temperature via retro Diels-Alder reaction, AB-, AB'C- and AB'CD-sequenced molecules polymerize into sequence-controlled polymers with corresponding sequences at 120 °C. Through this strategy, the synthesis of molecular modules does not require separation and purification, and sequence-controlled polymers with specific sequence can be synthesized in a one-pot process via adding different monomers and adjusting reaction condition.

Stimuli-responsive polymeric vesicles have attracted great attention in drug delivery due to their intrinsic hollow structures and “on demand” release of drugs upon environmental stimuli. The drug-release kinetics from polymeric vesicles, which is usually dependent on the stimuli-responsive behaviors of the polymeric vesicle, has great impacts on the therapeutic efficacy. Over the past decade, polymerization-induced self-assembly (PISA) has been demonstrated to be a powerful strategy to prepare the polymeric vesicles. However, fabrication of stimuli-responsive vesicles with adjustable drug release kinetics via PISA has been rarely reported, which may be due to the poor selectivity of functional membrane-forming polymers in the PISA system. Herein, a series of vesicles with different pH-responsive behaviors were fabricated via RAFT dispersion copolymerization of (diisopropylamino)ethyl methacrylate (DIPEMA) and benzyl methacrylate (BzMA). Both the content of DIPEMA units in hydrophobic P(DIPEMA-co-BzMA) bl...

Polymerization-induced self-assembly (PISA) has been established as a powerful strategy for fabrication of polymeric nano-objects in the past decade. However, in comparison with the traditional self-assembly method, PISA is unsatisfactory in preparation of vesicles with chemical versatility of membrane-forming block for tunable membrane properties, which limits the further application of PISA-based vesicles. Besides the stimuli-responsive property, structural integrity of the vesicles is another important concern for material applications. In situ cross-linking in PISA via copolymerization with multivinyl comonomers (cross-linkers) seems to be a straightforward and convenient method to afford stabilized nano-objects. However, it is hard to fabricate vesicles with cross-linked membrane via in situ cross-linking strategy because cross-linking greatly limits chain mobility of the produced copolymers and thus prevents morphology transition to form vesicles. In this article, in situ cross-linking in PISA for f...

Multicyclic polystyrene (PS) with hyperbranched structure was constructed in an efficient way. First, a seesaw-type PS was synthesized via atom transfer radical polymerization (ATRP) using a Y-shaped ATRP initiator containing one hydroxyl at center and bromine at each end. After azidation, the anthryl and hydroxyl groups were introduced to the ends of the polymer chain by click reaction with a trifunctional molecule bearing alkynyl, hydroxyl, and anthryl groups (alkynyl-OH-ant). By irradiation with 365 nm UV light in a highly dilute condition, cyclic polymer with three hydroxyl groups (c-PS-(OH)3) can be obtained; then it was converted to a cyclic polymer containing three azides (c-PS-(N3)3) by bromination of the hydroxyl groups and azidation. This “A3” cyclic macromonomer was then used to construct hyperbranched multicyclic polymers via self-accelerating click reaction with sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DBA). The properties of obtained polymer were characterized by NMR, FT-IR, MALDI-TOF MS, a...

Although the preparation of nano-objects by emulsifier-free controlled/living radical emulsion polymerization has drawn much attention, the morphologies of these formed objects are difficult to predict and to reproduce because of the much more complex nucleation mechanisms of emulsion polymerization compared to only one self-assembling nucleation mechanism of controlled radical dispersion polymerization. The present study compares dispersion polymerization with emulsifier-free emulsion polymerization in terms of nucleation mechanism, polymerization kinetics, and disappearance behavior of the macrochain transfer agent, gel permeation chromatograms curves of the obtained block copolymer as well as the structural and morphological differences between the produced nano-objects on the basis of published data. Moreover, the effects of the inherently heterogeneous nature of emulsion polymerization on the mechanism of reversible addition-fragmentation transfer polymerization and the nano-object morphology are examined, and efficient agitation and adequate solubility of the core-forming monomer in water are identified as the most crucial factors for the fabrication of nonspherical nano-objects.

By combination of high trapping radical efficiency of thioketone with resonance of allylic radicals, a novel mediated agent, 1, 3, 3-triphenylprop-2-ene-1-thione (TPPT) has been successfully synthesized. 1H NMR method was used to trace the TPPT-mediated radical polymerization of butyl acrylate (BA) at 50 °C, we observed that the disappearance rates of BA, TPPT and initiator, dimethyl 2,2′-azobis (2-methylpropionate) (AIBME) have the following order: BA > AIBME > TPPT, monomer conversion increases gradually with proceeding of the polymerization and approximately 84% of conversion was obtained within 24 h of the polymerization. The molecular weights of the obtained PBA are not varied obviously with the conversion, but the molecular weight distributions are narrow. The matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) studies reveal three polymerization mechanisms. The TPPT can efficiently capture the growing PBA radicals to form PBA-TPPT• radicals, and this highly stable radicals are able to be cross-terminated by the growing PBA• radicals or primary radicals to form the dormant chains. Although the reversed reaction of reaction 1 is very slow, the extension polymerization of the PBA can undergo to form block copolymers. The molecular weight of the formed PBA is influenced by the feed molar ratio of BA/TPPT and TPPT/AIBME.

A simple and efficient method to construct a hyperbranched multicyclic polymer is introduced. First, a tailored trithiocarbonate with two terminal anthracene units and three azide groups is successfully synthesized, and this multifunctional trithiocarbonate is used as chain transfer agent (CTA) to afford anthracene-telechelic polystyrene (PS) via reversible addition-fragmentation chain transfer (RAFT) polymerization. After that, linear PS is irradiated under 365 nm UV light to achieve the cyclization process. The monocyclic polymer further reacts with sym-dibenzo-1,5-cyclooctadiene-3,7-diyne via "A2 +B3 " strategy based on a self-accelerating click reaction to produce hyperbranched multicyclic polymer. The structures and properties of the polymers are characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), UV-vis spectrophotometry, and triple-detection size-exclusion chromatography (TD-SEC). The number of monocyclic units of the resultant hyperbranched multicyclic polymer reaches about 21 based on multi-angle laser light scattering (MALLS) measurements. The plot of intrinsic viscosity versus molecular weight reveals that the α value of the unique hyperbranched multicyclic polymer is lower than both hyperbranched polymers and cyclic polymers.

Polymerization-induced self-assembly (PISA) is an efficient and robust strategy to fabricate polymeric nano-objects. PISA enables us to prepare polymeric nano-objects in situ during the course of polymerization in concentrated solution (up to 50% w/w), making industrial production of polymeric assemblies in large-scale possible. In this work, reversible addition-fragmentation chain transfer (RAFT) dispersion copolymerization of styrene (St) and N-methacryloxysuccinimide (NMAS) was conducted with poly(2-hydroxyethyl acrylate) (PHEA) as a macro-chain transfer agent (macro-CTA) in methanol. Compared with the PHEA-mediated alcoholic dispersion polymerization of St, RAFT dispersion copolymerization of St and NMAS promoted morphology transition of nano-objects to form higher order morphologies (such as worms and vesicles). Moreover, the introduction of NMAS units into the solvophobic blocks provided functional handles for post-PISA modification of the resultant nano-objects via the active ester-amine reaction. The reaction of 1,6-hexanediamine with NMAS units in P(St-co-NMAS) blocks was conducted to afford cross-linked nano-objects with robust structural stability.

A visible light mediated reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) is conducted in ethanol using poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) as a macro-chain transfer agent (macro-CTA), affording polymeric nanomaterials with various morphologies. Unlike the polymerization-induced self-assembly and reorganization (PISR) process initiated by thermal stimuli, the photo-controlled PISR can be performed under more mild conditions, such as visible light and room temperature. Photoredox catalysis is employed to regulate the polymerization via a photoinduced electron transfer (PET) process. It is observed that the polymerization can be affected by catalyst concentration and light intensity, and “ON/OFF” control over polymerization is also demonstrated.

A highly efficient strategy, polymerization-induced self-assembly (PISA) for fabrication of the polymeric drug delivery systems in cancer chemotherapy is reported. Diblock prodrug copolymer, PEG-b-P(MEO2MA-co-CPTM) was used as the macro-RAFT agent to fabricate prodrug nanoparticles through PISA. The advantages of fabricating intelligent drug delivery system via this approach are as following: (1) Simultaneous fulfillment of polymerization, self-assembly, and drug encapsulation in one-pot at relatively high concentration (100 mg/mL); (2) Almost complete monomer conversion allows direct application of the resultant prodrug nanoparticles without further purification; (3) Robust structures of the resultant prodrug nanoparticles, because the cross-linker was used as the comonomer, resulted in core-cross-linking simultaneously with the formation of the prodrug nanoparticles; (4) The drug content in the resultant prodrug nanoparticles can be accurately modulated just via adjusting the feed molar ratio of MEO2MA/CPTM in the synthesis of PEG-b-P(MEO2MA-co-CPTM). The prodrug nanoparticles with similar diameters but various drug contents were obtained using different prodrug macro-CTA. In consideration of the long-term biological toxicity, the prodrug nanoparticles with higher drug content exhibit more excellent anticancer efficiency due to that lower dosage of them are enough for effectively killing HeLa cells.

Cyclic polystyrene (PS) with a pendant coumarin group is prepared by the combination of atom transfer radical polymerization and "click" chemistry. Fluorescence resonance energy transfer process is observed in the fluorescence measurement of coumarin-containing PS, and cyclic PS exhibits stronger emission than that of its linear precursor. When cyclic PS is irradiated under UV light at λ = 365 nm, 8-shaped PS is achieved due to the dimerization of pendant coumarin group. Subsequently, 8-shaped PS can be divided into single macrocycle under UV irradiation at λ = 254 nm via the photocleavage of coumarin dimer. The photoinduced coupling and dissociation are monitored by UV/vis spectra and gel permeation chromatography (GPC).

Graft copolymers with pendant macrocycles were synthesized via “graft onto” method. First, cyclic polystyrene (PS) was achieved by the combination of atom transfer radical polymerization (ATRP) and Cu-catalyzed azide–alkyne cycloaddition (CuAAc), and then an alkynyl group was introduced to cyclic PS. Meanwhile, poly(3-azide-2-hydroxypropyl methacrylate) (PGMA-N 3 ) was synthesized by ATRP of glycidyl methacrylate (GMA) and successive ring-opening of pendant epoxide ring with NaN 3 . The graft copolymer was achieved by the following click reaction between PGMA-N 3 and alkynyl-containing cyclic PS. GPC and 1 H NMR were utilized to characterize the obtained graft copolymers, and a maximal grafting density of 20% was observed. Thermal behaviors of linear PS, cyclic PS and PGMA grafted with cyclic PS (PGMA-g-cPS) were investigated by differential scanning calorimeter (DSC), and T g of PGMA-g-cPS is higher than those of linear and cyclic PS.

An ingenious formulation of RAFT dispersion polymerization based on photosensitive monomers of 2-nitrobenzyl methacrylate (NBMA) and 7-(2-methacryloyloxy-ethoxy)-4-methyl-coumarin (CMA) is reported herein. Various morphologies, such as spherical micelle, nanoworm, lamella, and vesicle, are fabricated at up to 20% solids content. Photoinduced cleavage of the NBMA moieties and dimerization of the coumarin moieties are simultaneously triggered upon UV (365 nm) irradiation. The former endows the cores of the nano-objects with abundant carboxyl groups, resulting in the transformation of the hydrophobic cores to hydrophilic ones. The latter induces the core-cross-linking of the nano-objects, which endows the nano-objects with enhanced structural stability and prevents the nanoparticle-to-unimer disassembly. The resultant nano-objects exhibit superior structural stability and excellent performances for drug delivery, including high drug loadings, pH-stimuli release, and high-efficient endosomal escape.

Different from concentric vesicles without spacing between the walls, the concentric vesicles with uniform spacing between the walls were rarely fabricated. We successfully fabricate the spaced concentric vesicles (SCVs) via RAFT dispersion polymerization, and continuous propagation of the residual polymer chains inside the large vesicles induces self-assembling to form SCVs. Concentration of the residual polymer chains in the solution of the nascent-formed vesicles is the determining factor for formation of SCVs, and continuous propagation of less or too more residual polymer chains will not form SCVs but form other morphologies. Generally, the concentration of the residual polymer chains after formation of vesicles is too low to self-assemble, so formation of SCVs is impossible. By adjusting the ratio of St/methanol or macro-RAFT agent P4VP-b-PS/P4VP, the concentration of residual polymer chains can be controlled, and further control of the morphologies is achieved. Formation of the inner vesicles by se...

Redox-responsive amphiphilic diblock copolymers, poly(6-O-methacryloyl-D-galactopyranose-co-2-(N,N-dimethylaminoethyl) methacrylate)-b-poly(pyridyl disulfide ethyl methylacrylate) (P(MAGP-co-DMAEMA)-b-PPDSMA) were obtained by deprotection of poly((6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-D-galactopyranose)-co-DMAEMA)-b-PPDSMA [P(MAlpGP-co-DMAEMA)-b-PPDSMA], which were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization of PDSMA using P(MAlpGP-co-DMAEMA) as macro-RAFT agent. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) studies showed that diblock copolymers P(MAGP-co-DMAEMA)-b-PPDSMA can self-assemble into micelles. Doxorubicin (DOX) could be encapsulated by P(MAGP-co-DMAEMA)-b-PPDSMA upon micellization and released upon adding glutathione (GSH) into the micelle solution. The galactose functional groups in the PMAGP block had specific interaction with HepG2 cells, and P(MAGP-co-DMAEMA)-b-PPDSMA can act as gene delivery vehicle. So, this kind of polymer has potential applications in hepatoma-targeting drug and gene delivery and biodetection.

A novel double-hydrophilic block copolymer P(MEO2MA-co-OEGMA)-b-PAMA has been successfully synthesized by two-step RAFT polymerization. Then, the amino groups of PAMA blocks in the copolymers react with 1-pyrenecarboxaldehyde via a “Schiff-base” reaction, and the resulting copolymers are self-assembled to form spherical micelles in aqueous solution. Because the “Schiff-base” linkage is pH sensitive, the release rate of pyrene depends upon the pH of solution. Complete release is achieved at pH 1, and the control release is much faster at pH 5.5 than that at pH 7.4. With progress of pyrene release, the micelles are disassembled gradually and disappeared completely at last. This double-hydrophilic copolymer is a promising candidate of drug carrier for the aldehyde- containing hydrophobic drugs.

A novel nanocontainer, which could regulate the release of payloads, has been successfully fabricated by attaching zwitterionic sulfobetaine copolymer onto the mesoporous silica nanoparticles (MSNs). RAFT polymerization is employed to prepare the hybrid poly(2-(dimethylamino)ethyl methacrylate)-coated MSNs (MSN-PDMAEMA). Subsequently, the tertiary amine groups in PDMAEMA are quaternized with 1,3-propanesultone to get poly(DMAEMA-co-3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate)-coated MSNs [MSN-Poly(DMAEMA-co-DMAPS)]. The zwitterionic PDMAPS component endows the nanocarrier with biocompatibility, and the PDMAEMA component makes the copolymer shell temperature-responsive. Controlled release of loaded rhodamine B has been achieved in the saline solutions.

Thermoresponsive double hydrophilic diblock copolymers poly(2-(2′-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate)-b-poly(6-O-methacryloyl-D-galactopyranose) (P(MEO2MA-co-OEGMA)-b-PMAGP) with various compositions and molecular weights were obtained by deprotection of amphiphilic diblock copolymers P(MEO2MA-co-OEGMA)-b-poly(6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-D-galactopyranose) (P(MEO2MA-co-OEGMA)-b-PMAlpGP), which were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization using P(MEO2MA-co-OEGMA) as macro-RAFT agent. Dynamic light scattering and UV–vis studies showed that the micelles self-assembled from P(MEO2MA-co-OEGMA)-b-PMAlpGP were thermoresponsive. A hydrophobic dye Nile Red could be encapsulated by block copolymers P(MEO2MA-co-OEGMA)-b-PMAGP upon micellization and released upon dissociation of the formed micelles under different temperatures. The galactose functional groups in the PMAGP block have specific interaction with HepG2 cells, and P(MEO2MA-co-OEGMA)-b-PMAGP has potential applications in hepatoma-targeting drug delivery and biodetection. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

The assembly behavior of diblock copolymers in solution can be modulated by block length, block ratio, solvent properties, and preparation route. Different assembly morphologies such as spherical micelles, cylindrical micelles, vesicles, and large compound vesicles have been obtained for diblock copolymers with shorter solvated block, such as poly(acrylic acid)-b-polystyrene (PAA-b-PSt). In the present work, we reported an easy-going route to prepare PAA-b-PSt assemblies with different morphologies through reversible addition−fragmentation-transfer (RAFT) dispersion polymerization of styrene in methanol with trithiocarbonated PAA as macromolecular chain transfer agent. Because this RAFT dispersion polymerization exhibited controlled features, the consecutive growth of PSt block led to the successive transition of the obtained PAA-b-PSt assemblies from spherical micelles, cylindrical micelles, vesicles, to large compound vesicles, confirmed by the combination of electron microscopy, laser light scattering,...

Various morphologies including spherical micelles, nanowires and vesicles have been prepared by reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of styrene (St) in methanol using S-1-dodecyl-S -(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (TC)-terminated poly(ethylene oxide) (PEO-TC) and 2,2′-azobis(isobutyronitrile) (AIBN) as chain transfer agent and initiator, respectively. GPC, 1H NMR, TEM and laser light scattering (LLS) were used to track the polymerization. The results showed that the block copolymers PEO-b-polystyrene (PEO-b-PS) were formed firstly in homogenous polymer solution, and then the spherical micelles were produced via polymerization-induced self-assembling. Continuous polymerization of the PS blocks induced the transition of spherical micelles into other morphologies. The polymerization-induced self-assembling and reorganization (PISR) were induced by chain length ratio increase of PS to PEO blocks. The concentration of St in methanol is also important factor to influence the formation of morphologies.

Drug delivery systems (DDS) based on functionalized polymeric nanoparticles have attracted considerable attention. Although great advances have been reported in the past decades, the fabrication efficiency and reproducibility of polymeric nanoparticles are barely satisfactory due to the intrinsic limitations of the traditional self-assembly method, which severely prevent further applications of the intelligent DDS. In the last decade, a new self-assembly method, which is usually called polymerization-induced self-assembly (PISA), has become a powerful strategy for the fabrication of the polymeric nanoparticles with bespoke morphology. The PISA strategy efficiently simplifies the fabrication of polymeric nanoparticles (combination of the polymerization and self-assembly in one pot) and allows the fabrication of polymeric nanoparticles at a relatively high concentration (up to 50 wt%), making it realistic for large-scale production of polymeric nanoparticles. In this review, the developments of PISA-based polymeric nanoparticles for drug delivery are discussed.

A water-soluble, biodegradable and fluorescent hyperbranched poly(amidoamine) with mannose groups on their surface (M-HPAMAM) has been successfully prepared, and the synthetic strategy includes Michael addition polymerization of diacrylamide with 1-(2-aminoethyl)piperazine and, subsequently, surface modification with mannosamine. The photoluminescence of M-HPAMAM was enhanced significantly due to the surface mannose groups. Incubation of E. coli with M-HPAMAMs yielded brightly fluorescent bacteria clusters, but the fluorescent intensity of the aqueous solution lowered. This indicates that the M-HPAMAMs have strong affinity with bacteria due to their polyvalent interactions. Based on the size and the amount of bacteria clusters formed, the bacteria with the concentrations higher than 10(2) cfu/mL can be detected.

A facile and feasible strategy for the preparation of vesicular morphologies has been developed using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymerization of styrene has been performed in a selected solvent, methanol, using S-1-dodecyl-S-(α,α'-dimethyl-α″-acetic acid)trithiocarbonate (TC)-terminated poly(4-vinylpyridine) as chain transfer agent and stabilizer. Various morphologies including spherical vesicles, nanotubes, and compound vesicles with different shapes are obtained by changing the feed ratios and reaction conditions. The final nanostructural materials are formed through formation of the block copolymers, self-assembly, and re-organization of the morphology in a one-pot polymerization. The latter two are induced by the propagation of PS blocks. The preparation of nanostructural materials can be performed at a concentration higher than 0.5 g · mL(-1) , thus this method offers a practical approach to prepare nanostructural materials on a large scale.

Hyperbranched poly(2-((bromobutyryl)oxy)ethyl acrylate) (HPBBEA) was grafted onto the exterior surface of mesoporous silica nanoparticles (MSNs) by surface-initiated self-condensing atom transfer radical vinyl polymerization (SCATRVP). The MSNs with ATRP initiator anchored on the exterior surface (MSN-Br) were prepared by the reaction of 5,6-dihydroxyhexyl-functionalized MSNs (MSN-OH) with α-bromoisobutyryl bromide. Afterwards, MSN-Br was utilized as initiator in the SCATRVP of inimer BBEA, resulting in core–shell nanoparticles with MSN core and HPBBEA shell (MSN-g-HPBBEA). The molecular weight of HPBBEA increased with the increasing ratio of BBEA to MSN-Br. In view of the high density of bromoester groups on the surface of HPBBEA shell, MSN-HPBBEA was used to initiate the successive polymerization of (2-dimethylamino-ethylmethacrylate) (DMAEMA), forming core–shell nanoparticles MSN-g-HPBBEA-g-PDMAEMA. The resultant products were characterized by FT-IR, NMR, HRTEM and thermogravimetric analysis (TGA), etc. The pH-responsive property of MSN-g-HPBBEA-g-PDMAEMA was characterized by measuring the hydrodynamics radius at different pH values, and this core–shell nanostructure may have potential applications in biomedicine and biotechnology.

Disulfide-functionalized hyperbranched poly(amido amine)s (HPAMAMs) were synthesized by Michael addition polymerization of N,N'-cystaminebisacrylamide and 1-(2-aminoethyl)piperazine. The novel HPAMAMs displayed bright fluorescence, and the emissions bands cover nearly the whole visible wavelength range. When polymer solutions were excited at 330-385, 460-490, and 510-550 nm, blue, green, and red solutions were observed, respectively. The HPAMAMs are biodegradable and they can be easily cleaved by 2-mercaptoethanol or glutathione, leading to a decrease in the fluorescence intensity. Studies of applications of the biocompatible and biodegradable HPAMAMs in fluorescence imaging technology and biological science are in progress.

Well-defined hyperbranched polystyrenes have been successfully prepared by polymerization of AB2 macromonomer, polystyrene containing an azide group at its one end and two terminal propargyl groups at the other end via click reaction. For preparation of AB2 macromonomers, an ATRP initiator, bispropargyl 2-bromosuccinate (BPBS) with two propargyl groups and one bromine group was synthesized by the successive bromination and esterification reaction of L-aspartic acid. The resulting BPBS initiated the ATRP of St, and subsequently, the terminal bromine groups of (CH≡C)2-PS-Brs were substituted by N3 via the reaction with sodium azide resulting the AB2 macromonomer, (CH≡C)2-PS-N3 with various molecular weights. All intermediates and the resultant polymers were characterized by GPC, 1H NMR, FTIR, and MALLS methods. The polymerization kinetics study showed fast increase of DP at the initial stage of polymerization and then slow increase of their DP. The final “HyperMacs” have high-molecular weight up to Mw,MALLS = 340,000 g/mol, their molecular weight distributions were moderately narrow (Mw/Mn = 1.47–1.65). The ratios of [η]H/[η]L of the HyperMacs formed in the polymerization system increased with evolution of polymerization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 454–462, 2010

A simple and unique strategy for preparation of large-compound vesicle (LCV)-encapsulated multiwalled carbon nanotubes (MWCNTs) has been developed, and this involves dispersion of MWCNTs in H-shaped copolymers solution in DMF and encapsulation of MWCNTs with LCVs formed from hydrolysis and polycondensation of Si(OCH3)3 groups in the amphiphilic H-shaped copolymers, (PTMSPMA)2PEG(PTMSPMA)2. This unique noncovalent approach is nondestructive, and the original structure of MWCNTs remains in the resultant MWCNTs/LCVs nanocomposites. The morphologies of nanocomposites LCVs/MWCNTs are controlled by the chain length ratio (NPTMSPMA/NPEG) of PTMSPMA to PEG. For the H-shaped copolymers with NPMSPMA/NPEG ≤ 1.7, they self-assembled to form LCVs with dense cavities in the presence of MWCNTs in a mixture of DMF/H2O. When this ratio was more than 2.0, the large-compound micelle-wrapped MWCNTs were produced. This approach is potentially useful for preparation of MWCNTs encapsulated with various morphologies of polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3669–3679, 2009

A series of well-defined θ-shaped copolymers composed of polystyrene (PS) and poly(e-caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution have been successfully synthesized without any purification procedure by the combination of atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP), and the “click” chemistry. The synthetic process involves two steps: (1) synthesis of AB2 miktoarm star copolymers, which contain one PCL chain terminated with two acetylene groups and two PS chains with two azido groups at their one end, (α,α′-diacetylene-PCL) (ω-azido-PS)2, by ROP, ATRP, and the terminal group transformation; (2) intramolecular cyclization of AB2 miktoarm star copolymers to produce well-defined pure θ-shaped copolymers using “click” chemistry under high dilution. The 1H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resultant intermediates and the target polymers. Their thermal behavior was investigated by DSC. The mobility decrease of PCL chain across PS ring in the theta-shaped copolymers restricts the crystallization ability of PCL segment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2620–2630, 2009

The thin films of a symmetric crystalline-coil diblock copolymer of poly(L-lactic acid) and polystyrene (PLLA-b-PS) formed lamellae parallel to the substrate surface in melt. When annealed at temperatures well above the glass transition temperature of PLLA block (T-g(PLLA)), the PLLA chains started to crystallize, leading to reorientation of lamellae. Such reorientation behavior exhibited dependence on the correlation between the crystallization temperature (T-c), the glass transition temperature of PS (T-g(PS)), the peak melting point of PLLA crystals (T-m(PLLA)), and the end melting point of PLLA crystals (T-m,end(PLLA)). When annealed at (T-c =) 80 degrees C (T-c < T-g(PS) < T-ODT, order-disorder transition temperature), 123 degrees C (T-g(PS) < T-c < T-m(PLLA) < T-ODT). 165 degrees C (T-g(PS) < T-m(PLLA) < T-c < T-m,end(PLLA) < T-ODT), the parallel lamellae became perpendicular to the substrate surface, exclusively starting at the edge of surface relief patterns. Meanwhile, the corresponding lamellar spacing was significantly enhanced.

The inverse star block copolymer, (poly(e-caprolactone)-b-polystyrene) 2 -core-(poly(e-caprolactone)-b-polystyrene) 2 , [(PCL-PS) 2 -core-(PCL-PS) 2 ] has been successfully prepared by combination of atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and "Click Chemistry." The synthesis includes the following five steps: (1) synthesis of a heterofunctional initiator with two ATRP initiating groups and two hydroxyl groups; (2) formation of (Br-PS) 2 -core-(OH) 2 via ATRP of styrene; (3) preparation of the (PCL-PS) 2 -core-(OH) 2 through "click" reaction of the α-propargyl, co-acetyl terminated PCL with (N 3 -PS) 2 -core-(OH) 2 which was prepared by transformation of the terminal bromine groups in (Br-PS) 2 -core-(OH) 2 into azide groups; (4) the ROP of CL using (PCL-PS) 2 -core-(OH) 2 as macroinitiator to form (PCL-PS) 2 -core-(PCL-OH) 2 ; and (5) preparation of the (PCL-PS) 2 -core-(PCL-PS) 2 through the ATRP of styrene using (PCL-PS) 2 -core-(PCL-Br) 2 as macroinitiator which was prepared by reaction of the terminal hydroxyl groups at the end of the PCL chains with 2-bromoisobutyryl bromide. The characterization data support structures of the inverse star block copolymer and the intermediates. The differential scanning calorimeter results and polarized optical microscope observation showed that the intricate structure of the inverse star block copolymer greatly restricted the movement of the PS segments and PCL segments, resulted in the increase of the glass transition temperature of PS segments and the decrease of crystallization ability of PCL segments.

The linear poly(e–caprolacton)-b-hyperbrached poly(2-((α-bromobutyryl)oxy)ethyl acrylate) (LPCL-b-HPBBEA) has been successfully synthesized by simultaneous ring-opening polymerization (ROP) of CL and self-condensing vinyl polymerization (SCVP) of BBEA in one-pot. The HPBBEA homopolymers were found to be formed in the polymerization because of the competitive reactions induced by initiation with bifunctional initiator, 2-hydroxylethyl-2′-bromoisobutyrate (HEBiB), and inimer BBEA. The separation of LPCL-b-HPBBEA from the polymerization products was achieved by precipitation in methanol. With feed ratio increase of CL and BBEA to HEBiB, the molecular weights of PCL and HPBBEA blocks in the block copolymer enhanced; and the polymerization rate of CL started to decrease gradually after 12 h of polymerization, but the polymerization rate of BBEA was maintained until 24 h of polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7628–7636, 2008

Well-defined hetero eight-shaped copolymers composed of polystyrene (PS) and poly(e-caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution were successfully synthesized by the combination of ring-opening polymerization, ATRP, and “click” reaction. The synthetic procedure involves three steps: (1) preparation of a tetrafunctional PS and PCL star copolymer with two PS and two PCL arms using the tetrafunctional initiator bearing two hydroxyl groups and two bromo groups; (2) synthesis of tetrafunctional star copolymer, (α-acetylene-PCL)2(ω-azido-PS)2, by the transition of terminal hydroxyl and bromo groups to acetylene and azido groups through the reaction with 4-propargyloxybutanedioyl chloride and NaN3 respectively; (3) intramolecular cyclization reaction to produce the hetero eight-shaped copolymers using “click” chemistry under high dilution. The 1H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resulted intermediates and the target polymers. Their thermal behavior was investigated by DSC, and their crystallization behaviors of PCL were studied by polarized optical microscopy. The decrease in chain mobility of the eight-shaped copolymers restricts the crystallization of PCL and the crystallization rate of PCL is slower in comparison with their corresponding star precursors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6496–6508, 2008

Well-defined figure-of-eight-shaped (8-shaped) polystyrene (PS) with controlled molecular weight and narrow polydispersities has been prepared by the combination of atom transfer radical polymerization (ATRP) and click chemistry. The synthesis involves two steps: 1) Preparation of a linear tetrafunctional PS with two azido groups, one at each end of the polymer chain, and two acetylene groups at the middle of the chain. 2) Intramolecular cyclization of the linear tetrafunctional PS at a very low concentration by a click reaction to produce the 8-shaped polystyrenes. The resulting intermediates and the target polymers were characterized by 1 H NMR and FT-IR spectroscopy, and gel permeation chromatography. The glass transition temperatures (T g s) were determined by differential scanning calorimetry and it was found that the decrease in chain mobility by cyclization resulted in higher T g s for 8-shaped polystyrenes as compared to their corresponding precursors.

A series of well-defined centipede-like copolymers with poly(glycidyl methacrylate) (PGMA) as main chain and poly(L-lactide) (PLLA) and polystyrene (PSt) as side chains have been synthesized successfully by combination of ring-opening polymerization and atom transfer radical polymerization (ATRP). The synthetic process includes three steps. (1) Synthesis of PGMA via ATRP; (2) preparation of macroinitiator with one bromine group and a hydroxyl group at every GMA unit of PGMA; (3) ring-opening polymerization of LLA and ATRP of St to obtain the asymmetric centipede-like copolymers. The number–average degrees of polymerization of PGMA backbone, PLLA and PSt side chains were determined by 1H-NMR spectra, and the molecular weights of the resultant intermediates and centipede-like copolymers were measured by gel permeation chromatography. The molecular weight distributions were narrow and the molecular weights of both the backbone and the side chains were controllable. The thermal behavior of the centipede-like copolymers was investigated by differential scanning calorimeter. With the increase of PSt side chain length, the glass transition temperature of PLLA side chains shifted to high temperature, and crystallization ability of PLLA side chains became poor. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5580–5591, 2008

The morphology of a H-shaped block copolymer (poly(ethylene glycol) backbone and polystyrene branches (PS)(2)PEG(PS)(2)) in a thin film has been investigated. A peculiar square lamella that has a phase-separated microdomain at its surface is obtained after spin coating. The experimental temperature plays a critical role in the lamellar formation. The copolymer first self-assembles into square lamellar micelles with an incomplete crystalline core due to the crystallizability of PEG.

Dendritic–linear–dendritic triblock copolymers composed of linear polystyrene (PSt) and poly(amidoamine) dendrons have been successfully synthesized. Two bromines-terminated PSt with Mn = 13,000 was prepared by atom transfer radical polymerization (ATRP) using α,α′-dibromo-p-xylene as initiator. Then the terminal bromines at both ends of PSt chains were replaced by one imine group of piperazine (PZ), and further Michael addition reaction of terminal PZ with excess 1,3,5-triacryloylhexahydro-1,3,5-triazine (TT) produced the first generation (G1) of the triblock copolymer. Continuous growth of dendrons from G1.5 to G4 at the both ends of PSt chains was carried out by the iterative Michael addition reactions with excess PZ and following TT. The ABA triblock copolymers composed of the G1–G4 dendrons and the linear PSt were obtained. Structures of the triblock polymers were characterized by GPC and 1H NMR spectra. Thermal phase transitions of the polymers were studied by DSC measurements, and all of the copolymers displayed a glass transition temperature.

Hyperbranched poly(amido amine)s containing vinyl and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with equal molar ratio in feed. 1H, 13C and HSQC NMR techniques were used to clarify the structure of hyperbranched polymers and polymerization mechanism. The Michael addition reaction of hyperbranched poly(1TT-1APD)s with primary amine-terminated poly(e-benzyloxycarbonyl- l -lysine)s [PLys(Z)] yielded a star-like hyperbranched polymers with poly(1TT-1APD) core and Plys(Z) shell. The Z groups in PLys(Z) were removed under acidolysis, and thus star-like hyperbranched polymers with hydroxyl groups inside and primary amine groups outside were obtained successfully.

A new dendritic heteroarm star copolymer that contains multi-alternating arms of poly(ethylene oxide-tetrahydrofuran) (P(EO-THF)) and poly(methyl methacrylate) (PMMA) on a dendritic polyester core has been synthesized by a 'core-first' approach by combination of sequential cationic ring-opening polymerization (CROP) and reversible addition-fragmentation transfer (RAFT) polymerization initiated by a dendritic macroinitiator (3) capped with multi-alternating terminal carboxylic acid groups (used directly to initiate the ROP of THF in the presence of EO as a polymerization promoter to attain P(EO-THF) arms) and dithio-benzoate groups (used to initiate RAFT polymerization of MMA to attain PMMA arms). The structures of the products were confirmed by NMR spectroscopy, GPC-MALLS, and DSC measurements.

Well-defined six-armed star poly(L-lactic acid) (PLLA) with a triphenylene core has been prepared by ring-opening polymerization of L-lactide. As a result of strong π-π interactions between the triphenylene core and the multi-walled carbon nanotubes (MWCNTs), the polymer was conveniently immobilized on the surface of the as-received MWCNTs by a simple ultrasonic process while the intrinsic graphitic structure of the pristine MWCNTs is retained. The non-covalent interaction between the carbon nanotubes and the polymer has been proven by the UV-vis absorption spectra, the fluorescence spectra, the Raman spectra, and the X-ray photoelectron spectra.

The three generations dendrimer-like copolymers C(PSt(PLLA(PSt–PNAS)2)2)3 and C(PSt(PLLA(PSt–PNAS)2)2)4 have been successfully synthesized by combination of ATRP and ROP. Diethanol amine and 2,2-bis(methylene-2-bromoisobutyrate) propionyl chloride (BMBIBPC) were used as divergent reagents, respectively, before preparations of the second and the third generations. The resultant polymers were characterized by GPC and 1H NMR. Then the outermost PSt–PNAS in the dendrimer-like copolymers was cross-linked via substitution reaction of NAS with ethylene diamine, and at the same time, the PLLA segments in the second generation were decomposed in dilute THF or CHCl3 solution, forming hollow particles. The resultant morphologies were characterized by SEM and DLS methods, and spherical particles with various sizes were observed. The hollow particles may have potential applications in catalysis and bioengineering.

Novel and well-defined pyrene-containing eight-arm star-shaped dendrimer-like copolymers were successfully achieved by combination of esterification, atom transfer radical polymerization (ATRP), divergent reaction, ring-opening polymerization (ROP), and coupling reaction on the basis of pentaerythritol. The reaction of pentaerythritol with 2-bromopropionyl bromide permitted ATRP of styrene (St) to form four-arm star-shaped polymer (PSt-Br)4. The molecular weights of these polymers could be adjusted by the variation of monomer conversion. Eight-hydroxyl star-shaped polymer (PSt-(OH)2)4 was produced by the divergent reaction of (PSt-Br)4 with diethanolamine. (PSt-(OH)2)4 was used as the initiator for ROP of e-caprolactone (CL) to produce eight-arm star-shaped dendrimer-like copolymer (PSt-b-(PCL)2)4. The molecular weights of (PSt-b-(PCL)2)4 increased linearly with the increase of monomer. After the coupling reaction of hydroxyl-terminated (PSt-b-(PCL)2)4 with 1-pyrenebutyric acid, pyrene-containing eight-arm star-shaped dendrimer-like copolymer (PSt-b-(PCL-pyrene)2)4 was obtained. The eight-arm star-shaped dendrimer-like copolymers presented unique thermal properties and crystalline morphologies, which were different from those of linear poly(e-caprolactone) (PCL). Fluorescence analysis indicated that (PSt-b-(PCL-pyrene)2)4 presented slightly stronger fluorescence intensity than 1-pyrenebutyric acid when the pyrene concentration of them was the same. The obtained pyrene-containing eight-arm star-shaped dendrimer-like copolymer has potential applications in biological fluorescent probe, photodynamic therapy, and optoelectronic devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2788–2798, 2008

The confined space produced during the polymerization has access for all small organic molecules or oligomers with small size to enter this confined space; however, it can prevent the macromolecules with big size from entering. Therefore, the reaction between two branched macromolecules is excluded in A2+B3 polymerization system, resulting uncrosslinked branched polymers, and there was no gel point observed throughout the polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1730–1737, 2008

Hyperbranched poly(glycidyl methacrylate) (PGMA) and poly(GMA-co-styrene) have been synthesized by the self-condensing vinyl polymerization of GMA and the copolymerization of GMA and St. Cp 2 Ti(III)Cl catalyzed the epoxy groups to produce initiating radicals and Cu(II)X 2 (X = Br or Cl) was used for control of the polymerization. The resultant polymers were characterized by GPC and 1 H NMR, and the molecular weights, the molecular weight distribution and the degree of branching were determined. The branching structure of the polymers was further confirmed by a hydrolysis test. Hyperbranched star polymers with HPGMA as the core and PSt as the arms were synthesized by the atom transfer radical polymerization of St using HPGMA as a macroinitiator. The resultant products were analyzed by GPC and 1 H NMR. Their morphology in solution was investigated by TEM. The hyperbranched polymers were modified by various acids and amines, and the variation in solution properties was investigated.