The development of phosphinoamine–Pd(II)–imidazole complexes: implications in room‐temperature Suzuki–Miyaura cross‐coupling reaction

The reaction of N‐methylimidazole (N‐MeIm) and N‐butylimidazole (N‐BuIm) with the complexes [PdCl₂(PPh₂py–P,N)] and [PdCl₂(PPh₂Etpy–P,N)] in the presence of NH₄PF₆ under N₂ at room temperature afforded four new cationic Pd(II) complexes [PdCl(PPh₂py–P,N)(N‐MeIm)](PF₆) ( 1 ), [PdCl(PPh₂py–P,N)(N‐BuIm)](PF₆) ( 2 ), [PdCl(PPh₂Etpy–P,N)(N‐MeIm)](PF₆) ( 4 ) and [PdCl(PPh₂Etpy‐P,N)(N‐BuIm)](PF₆) ( 5 ) in good yields, where PPh₂py is 2‐(diphenylphosphino)pyridine and PPh₂Etpy is 2‐{2‐(diphenylphosphino)ethyl}pyridine). The complexes were fully characterized. The catalytic activities of these complexes were investigated for Suzuki–Miyaura cross‐coupling reactions at room temperature. Complex 2 exhibited excellent activity compared to other analogs. Copyright © 2013 John Wiley & Sons, Ltd.     

Homogeneous radical polymerization of 2‐hydroxyethyl methacrylate mediated by cyclometalated cationic Ruthenium(II) complexes with PF6− and Cl− in protic media

Cationic coordinatively saturated complexes of ruthenium(II), [Ru(o‐C₆H₄‐2‐py)(phen)(MeCN)₂]⁺, bearing different counterions of PF₆^? and Cl^? have been used in the radical polymerization of 2‐hydroxyethyl methacrylate in protic media and acetone under homogeneous conditions. Exchange of PF₆^? by Cl^? increases the solubility of the complex in water. Both complexes led to the fast polymerization under mild conditions, but control was achieved only in methanol and acetone and was better for the complex with Cl^?. The polymerization accelerated in aqueous media and proceeded to a high conversion even with a monomer/catalyst = 2000/1, but without control. Polymerization mediated by complex bearing Cl^? was slower in protic solvents but faster in acetone and always resulted in lower molecular weight polymers. Thus, the nature of the anion strongly affected the catalytic activity of the complexes and may serve as way of fine‐tuning the catalytic properties. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Modulating structural stability and acid sensitivity of photosensitive polymer micelles simply via one‐batch UV irradiation

This article describes the photosensitive polymer micelles whose structural stability and acid sensitivity can be widely tuned simply via one‐batch UV irradiation. To this end, the well‐defined poly(5‐ethyl‐5‐methacryloyloxy‐methyl‐2‐styryl‐[1,3]dioxane)‐block‐poly[poly(ethylene glycol) methacrylate] (PEMSD‐b‐PPEGMA) copolymers were synthesized via RAFT polymerization under mild visible light radiation at 30 °C. The results demonstrated that the irradiation of the homogeneous acetone solution with UV light only induced Z‐isomerization of their cinnamyl groups, while irradiating PEMSD chains in the bulky micellar cores only induced dimerization. Moreover, the micelles of previously Z‐isomerized copolymer could be effectively stabilized without changing their acid sensitivity on irradiating for shortly 3 min, while UV irradiation for 30 min could remarkably improve the acid stability of these micelles. These novel properties are of potential applications in controlled drug delivery. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Hybrid acrylate‐oxetane photopolymerizable systems

Simultaneous free radical and cationic photopolymerizations of mixtures of multifunctional acrylate and oxetane monomers were carried out to provide hybrid interpenetrating network polymers. The use of “kick‐started” oxetanes in which oxetane monomers are accelerated by the use of small amounts of certain highly substituted epoxides provides dual independent radical and cationic systems with similar rates of photopolymerization leading to homogeneous interpenetrating networks. The combined photopolymerizations are very rapid and afford crosslinked network films that are colorless, hard, and transparent. The networks display no indications of phase separation. The use of this technology in various applications such as coatings, 3D imaging, and for composites is discussed. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 594–601     

Strong and tough hydrogels crosslinked by multi-functional polymer colloids

Tough polymer hydrogels have great potential applications in soft actuators, artificial muscles, tissue engineering, and so forth. To improve the strength and toughness of hydrogels, numerous strategies have been developed to integrate efficient energy dissipation mechanisms into the hydrophilic networks. Among them, the use of macro-crosslinkers to replace conventional chemical ones has become promising to develop tough hydrogels. Polymer colloids—including nano-/microparticles, nano-/microgels, hydrophobic associates, and block copolymer assemblies—have been employed in literature as multi-functional macro-crosslinkers that link polymer chains through covalent bonds or noncovalent interactions. The dislocation, deformation, desociation, and rupture of polymer colloids upon loadings are the major mechanisms to dissipate energy. This article provides a comprehensive account of most recent progresses on tough hydrogels crosslinked by polymer colloids, and explores the toughening mechanisms. It aims to inspire novel designs of tough hydrogels with multi-functionalities. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1336–1350     

From toroidal to rod‐like nanostructure,a mechanism study for the reversible morphological control on amphiphilic triblock copolymer micelles

Mechanism of the morphological changes between toroidal and rod‐like nanostructures of P4VP‐b‐PS‐b‐P4VP amphiphilic triblock copolymer micelles has been investigated in aqueous solution. This transition is proved to be highly reversible and tunable upon changing temperature. The toroidal structure, evolving from fibers at 20 °C, can transform to rod‐like morphology as the temperature either gradually or directly increases to 80 °C, and vice versa. However, the transition mechanisms are quite different in different temperature‐changing processes. The structure and thickness of the micelles are dependent on the specific temperature, whereas the transition mechanism is related to the method of the temperature change. These morphological changes are considered as a result from the interaction parameter between the solvent and the copolymer blocks, especially the hydrophobic block. Our research complements the external control over the reversible morphological transition of block copolymer micelles without changing the composition of the system or introducing additional influencing factors. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1450–1457     

Reversible Morphological Evolution of Responsive Giant Vesicles to Nanospheres by the Self‐Assembly of Crystalline‐b‐Coil Polyphosphazene Block Copolymers

The preparation of long‐term‐stable giant unilamellar vesicles (GUVs, diameter ≥1000 nm) and large vesicles (diameter ≥500 nm) by self‐assembly in THF of the crystalline‐b‐coil polyphosphazene block copolymers [N=P(OCH₂CF₃)₂]_n‐b‐[N=PMePh]_m ( 4 a : n=30, m=20; 4 b : n=90, m=20; 4 c : n=200, m=85), which combine crystalline [N=P(OCH₂CF₃)₂] and amorphous [N=PMePh] blocks, both of which are flexible, is reported. SEM, TEM, and wide‐angle X‐ray scattering experiments demonstrated that the stability of these GUVs is induced by crystallization of the [N=P(OCH₂CF₃)₂] blocks at the capsule wall of the GUVS, with the [N=PMePh] blocks at the corona. Higher degrees of crystallinity of the capsule wall are found in the bigger vesicles, which suggests that the crystallinity of the [N=P(OCH₂CF₃)₂] block facilitates the formation of large vesicles. The GUVs are responsive to strong acids (HOTf) and, after selective protonation of the [N=PMePh] block, they undergo a morphological evolution to smaller spherical micelles in which the core and corona roles have been inverted. This morphological evolution is totally reversible by neutralization with a base (NEt₃), which regenerates the original GUVs. The monitoring of this process by dynamic light scattering allowed a mechanism to to be proposed for this reversible morphological evolution in which the block copolymer 4 a and its protonated form 4 a⁺ are intermediates. This opens a route to the design of reversibly responsive polymeric systems in organic solvents. This is the first reversibly responsive vesicle system to operate in organic media.     

Synthesis of amphiphilic copolymer having acid‐labile bicyclo bisoxazolidine in the side chain for controlled release of fragrance aldehyde

A metharylate monomer having an octanal‐derived bicyclo bisoxazolidine (BBOX) moiety was synthesized and was radically copolymerized with a methacrylate having a hydrophilic poly(ethylene glycol) chain to obtain an amphiphilic copolymer having the BBOX moieties as hydrophobic side chains. The BBOX moieties were stable for 7 days at pH 7.0, whereas they were gradually hydrolyze at pH 5.0 to release octanal continuously for 7 days, confirming the potential applicability of the copolymer to a polymeric pro‐fragrance that can release aldehyde‐type fragrance molecules slowly for a long period. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Radical‐cured block copolymer‐modified thermosets

Poly(ethylene‐alt‐propylene)‐b‐poly(ethylene oxide) (PEP‐PEO) diblock copolymers were synthesized and added at 4 wt % to 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy)phenyl]propane (BisGMA), a monomer that cures using free radical chemistry. In separate experiments, poly(ethylene glycol) dimethacrylate (PEGDMA) was combined as a secondary monomer with BisGMA and the monomers were loaded with 4 wt % PEP‐PEO. The diblock copolymers self‐assembled into well‐dispersed spherical micelles with PEP cores and PEO coronas. No appreciable change in the final extent of cure of the thermosets was caused by the addition of diblock copolymer, except in the case of BisGMA, where the addition of the block copolymer increased extent of cure by 12%. Furthermore, the extent of cure was increased by 29% and 37% with the addition of 25 and 50 wt % PEGDMA, respectively. Elastic modulus and fracture resistance were also determined, and the values indicate that the addition of block copolymers does not significantly toughen the thermoset materials. This finding is surprising when compared with the large increase in fracture resistance seen in block copolymer‐modified epoxies, and an explanation is proposed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Synthesis,self‐assembly,and formation of photo‐crosslinking‐stabilized fluorescent micelles covalently containing zinc(II)‐bis(8‐hydroxyquinoline) for ABC triblock copolymer bearing cinnamoyl and 8‐hydroxyquinoline side groups

Triblock copolymers (MPEG‐b‐PCEMA‐b‐PHQHEMA) bearing cinnamoyl and 8‐hydroxyquinoline side groups with different block length are synthesized by a two‐step reversible addition fragmentation chain transfer polymerization of cinnamoyl ethyl methacrylate (CEMA) and 2‐((8‐hydroxyquinolin‐5‐yl)methoxy)ethyl methacrylate (HQHEMA), respectively. The self‐assembly of MPEG‐b‐PCEMA‐b‐PHQHEMA in mixture of THF and ethanol is investigated by varying the ratio of THF and ethanol. Spheric micelles with diameter of 63.7 nm and polydispersity of 0.128 are obtained for MPEG₁₁₃‐b‐PCEMA₁₅‐b‐PHQHEMA₁₇ in THF/ethanol with a volume ratio (v/v) of 5/5. The PCEMA inner shell of the resulted micelles is photo‐crosslinked under UV radiation to give stabilized micelles. The complex reaction of the stabilized micelles with Zn(II) is investigated under different conditions to give zinc(II)‐bis(8‐hydroxyquinoline)(Znq₂)‐containing micelles. When the complex reaction is carried out in THF/ethanol (v/v = 5/5) or THF/toluene (v/v = 6/4) with zinc acetate, fluorescent Znq₂‐containing micelles are obtained without obvious change in diameters and morphologies. The fluorescent micelles exhibit green emission with λ_max at 520 nm. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1056–1064