Linear Azo Polymer Containing Conjugated 5,5′‐Azodisalicylic Acid Segments in the Main Chain: Synthesis,Characterization, and Degradation

Summary: Copolymers of poly(ethylene oxide) (PEO) and 5,5′‐azodisalicylic acid (Olsalazine, OLZ) were synthesized and evaluated by hydrolysis and in‐vitro biodegradation with azoreductase. It was found that changing the molecular weight of the PEO blocks affected the loading ratio of OLZ, and resulted in significant differences in the hydration and degradability of the copolymers. These novel azo‐containing copolymers can be used in colon‐specific drug delivery.

Release of 5‐ASA from OLZ and PEO‐OLZ copolymers incubated with rat cecum content in the presence of benzyl viologen and α‐D ‐glucose.     

Emulsion‐Induced Ordered Microporous Films Based on Micelles of Amphiphilic Poly(ethylene oxide)‐block‐Poly(methyl methacrylate) Diblock Copolymers

Well‐defined PEO‐b‐PMMA was prepared, initiated by macroinitiator PEO‐Br, by means of ATRP, where esterification of the terminal hydroxyl group of PEO with 2‐bromoisobutyryl bromide yielded a macroinitiator PEO‐Br. Highly ordered microporous films (hexagonal pattern) were constructed by emulsion micelles of such amphiphilic diblock copolymer formed from a solution with CHCl₃/H₂O/THF = 100:5:10 (v/v). We also constructed the microporous films using diblock copolymer by the current water‐assisted method.

     

Synthesis of a Novel ABC Triblock Copolymer with a Rigid‐Rod Block via Atom Transfer Radical Polymerization

Summary: A novel ABC triblock copolymer with a rigid‐rod block was synthesized by atom transfer radical polymerization (ATRP). First, a poly(ethylene oxide) (PEO)‐Br macroinitiator was synthesized by esterification of PEO with 2‐bromoisobutyryl bromide, which was subsequently used in the preparation of a poly(ethylene oxide)‐block‐poly(methyl methacrylate) (PEO‐b‐PMMA) diblock copolymer by ATRP. A poly(ethylene oxide)‐block‐poly(methyl methacrylate)‐block‐poly{2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene} (PEO‐b‐PMMA‐b‐PMPCS) triblock copolymer was then synthesized by ATRP using PEO‐b‐PMMA as a macroinitiator.

ABC triblock copolymer with a rigid‐rod block.     

Synthesis of Poly(ethylene oxide)s Bearing Functional Groups along the Chain

Well‐defined poly(ethylene oxide)s (PEOs) bearing reactive sites regularly distributed along the chain have been synthesized by the polycondensation of PEO containing a central tertiary amino group with dichloromethane, followed by quaternization with suitable reagents to obtain polyzwitterionic or cationic PEOs with alkyl, allyl, or fluorocarbon pendant groups. The pendant allyl groups have been converted into primary amino groups by reaction with 2‐aminoethanethiol hydrochloride to obtain polyamino‐functionalized PEO.

Polyfunctional PEOs bearing different pendant groups.     

A Bioinspired Polymeric Template for 1D Assembly of Metallic Nanoparticles,Semiconductor Quantum Dots,and Magnetic Nanoparticles

A precise control of metallic‐nanoparticle assembly is highly critical for the realization of tangible, high‐performance devices or materials. Until recently, nanoparticle assembly using 1D templates had been limited to a narrow spectrum of nanoparticles as it was mostly dependent on the surface chemistry of the nanoparticles used. Inspired by the universal adhesive properties of mussels, we demonstrate a universal polymeric template for 1D assembly of various nanoparticles including, gold nanoparticles, iron oxide nanoparticles, and quantum dots. We find that the length of the 1D assembly is tunable using hyaluronic acid‐graft‐catechol templates with various contour lengths.

     

Uniform PEO Star Polymers Synthesized in Water via Free Radical Polymerization or Atom Transfer Radical Polymerization

Amphiphilic star shaped polymers with poly(ethylene oxide) (PEO) arms and cross‐linked hydrophobic core were synthesized in water via either conventional free radical polymerization (FRP) or atom transfer radical polymerization (ATRP) techniques using a simple “arm‐first” method. In FRP, PEO based macromonomers (MM) were used as arm precursors, which were then cross‐linked by divinylbenzene (DVB) using 2,2′‐azoisobutyronitrile (AIBN). Uniform star polymers ( < 1.2) were achieved through adjustment of the ratio of PEO MM, DVB, and AIBN. While in case of ATRP, both PEO MM, and PEO based macroinitiator (MI) were used as arm precursors with ethylene glycol diacrylate as cross‐linker. Even more uniform star polymers with less contamination by low MW polymers were obtained, as compared to the products synthesized by FRP.

     

Multifunctional Poly(N‐vinylcarbazole)‐Based Block Copolymers and their Nanofabrication and Photosensitizing Properties

The synthesis of poly(N‐vinylcarbazole)‐based block copolymers functionalized with rhenium diimine complexes or pendant terpyridine ligands is reported. The copolymers are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization, and they exhibit interesting morphological properties as a result of the phase separation between different blocks. The rhenium complex polymer block may function as a photosensitizer, while the terpyridine‐containing polymer block can be used as the template for nanofabrication by selective deposition of zinc complexes.

     

Synthesis,Characterization and Self‐Assembly of Novel Amphiphilic Block Copolymers with a Polyhedral Oligomeric Silsesquioxanes Moiety Attached at the Junction of the Two Blocks

A novel well‐defined amphiphilic block copolymer, with the polyhedral oligomeric silsesquioxane (POSS) moiety at the junction of the two blocks of polystyrene and poly(ethylene oxide) (PEO), was designed and synthesized. First, a macroinitiator containing a POSS moiety and a PEO chain was prepared and then atom transfer radical polymerization of styrene was carried out in the presence of the macroinitiator in bulk. The polymerization results show that the process bears the characteristics of controlled/living free radical polymerizations. The structure and molecular weight of the polymers were characterized by GPC, ¹H NMR, and FT‐IR spectroscopy. The self‐assembly behaviors of the polymers was investigated by TEM and SEM. It was observed that the polymers can self‐assemble into vesicles in aqueous solution.

     

Synthesis and Characterization of α,ω‐Heterofunctional Poly(ethylene oxide) Macromonomers

A novel α,ω‐heterofunctional poly(ethylene oxide) (PEO) macromonomer possessing methacryloyl and thienyl end groups was prepared by ring‐opening polymerization of ethylene oxide initiated by potassium thienylethoxide and termination of the living PEO ends with methacryloyl chloride. Incorporation of methacryloyl and thienyl groups was confirmed by free‐radical and oxidative polymerization processes, respectively, and by means of ¹H NMR analysis.

     

Hairy PEO‐Silica Nanoparticles through Surface‐Initiated Polymerization of Ethylene Oxide

Summary: The grafting of poly(ethylene oxide) (PEO) onto silica nanoparticles was performed in situ by the ring‐opening polymerization of the oxirane monomer initiated from the mineral surface using aluminium isopropoxide as an initiator/heterogeneous catalyst. Alcohol groups were first introduced onto silica by reacting the surfacic silanols with prehydrolyzed 3‐glycidoxypropyl trimethoxysilane. The alcohol‐grafted silica played the role of a coinitiator/chain‐transfer agent in the polymerization reaction and enabled the formation of irreversibly bonded polymer chains. Silica nanoparticles containing up to 40 wt.‐% of a hairy layer of grafted PEO chains were successfully produced by this technique.

The grafting of poly(ethylene oxide) (PEO) onto silica nanoparticles by in‐situ ring‐opening polymerization of the oxirane monomer.     

Polyglycidol Based Amphiphilic Double‐Comb Copolymers and Their Self‐Association in Aqueous Solution

Herein, we report synthesis and self‐association properties of amphiphilic double‐comb polymers with polyglycidol backbones. First, a bifunctional polyglycidol precursor is synthesized via monomer activated anionic polymerization. Next, two efficient and orthogonal polymer analogous reactions are carried out for grafting hydrophilic oligoethylene glycol side chains and hydrophobic linear aliphatic side‐chains. The polymers are analyzed by means of NMR, GPC, and DSC. From the DSC analysis of the bulk samples it is evident that aliphatic side chains segregate from the polar backbone and thus crystallize. Furthermore, in aqueous media the double‐comb polymers spontaneously self‐assemble to form a multilayer structure. The present results pave a way to tailor and design amphiphilic polymers based on glycidols. Major advantages are spontaneous self‐assembly in water and the possibility to form onion polymersomes relevant to encapsulation.

     

Synthesis of Eight‐shaped Poly(ethylene oxide) by the Combination of Glaser Coupling with Ring‐opening Polymerization

The eight‐shaped poly(ethylene oxide) (PEO) is synthesized by a combination of Glaser coupling with ring‐opening polymerization (ROP). Firstly, the star‐shaped (PEO‐OH) ₄ is synthesized by ROP of ethylene oxide (EO) using pentaerythritol as an initiator and diphenylmethyl potassium (DPMK) as a deprotonated agent, and then the alkyne group is introduced onto the PEO arm‐end to give (PEO‐Alkyne) ₄ in a NaH/tetrahydrofuran (THF) system. The intramolecular cyclization is carried out by a Glaser coupling reaction in a pyridine/CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) system at room temperature in an air atmosphere, and eight‐shaped PEO was formed with high efficiency (almost 100%). The target polymers and intermediates were well characterized by SEC, MALDI‐TOF MS, ¹H NMR and FT‐IR in detail.

     

Preparation of Star‐Shaped ABC Copolymers of Polystyrene‐Poly(ethylene oxide)‐Polyglycidol Using Ethoxyethyl Glycidyl Ether as the Cap Molecule

The 3‐miktoarm star‐shaped ABC copolymers of polystyrene–poly(ethylene oxide)–poly(ethoxyethyl glycidyl ether) (PS‐PEO‐PEEGE) and polystyrene–poly(ethylene oxide)–polyglycidol (PS‐PEO‐PG) with low polydispersity indices (PDI ≤ 1.12) and controlled molecular weight were synthesized by a combination of anionic polymerization with ring‐opening polymerization. The polystyryl lithium (PS⁻Li⁺) was capped by EEGE firstly to form the functionalized polystyrene (PS_A) with both an active ω‐hydroxyl group and an ω′‐ethoxyethyl‐protected hydroxyl group, and then the PS‐b‐PEO block copolymers, star(PS‐PEO‐PEEGE) and star(PS‐PEO‐PG) copolymers were obtained by the ring‐opening polymerization of EO and EEGE respectively via the variation of the functional end group, and then the hydrolysis of the ethoxyethyl group on the PEEGE arm. The obtained star copolymers and intermediates were characterized by ¹H NMR spectroscopy and SEC.

     

Dewetting and Phase Behaviors for Ultrathin Films of Polymer Blend

Summary: Dynamics of dewetting and phase separation in ultrathin films (thickness is ca. one radius of gyration, ≈1 R_g) of poly(methyl methacrylate) (PMMA) and poly(styrene‐ran‐acrylonitrile) (SAN) blends on Si substrate has been studied by in situ atomic force microscopy (AFM). In the miscible region, a “spinodal‐like” dewetting driven by a composition fluctuation recently predicted by Wensink and Jérôme (Langmuir 2002 , 18, 413) occurs. In the two‐phase region, the dewetting of the whole film is followed by phase separation in the droplets, coupling with the wetting of the substrate by the PMMA extracted by the strong attractive interaction between them.

     

Functionalization of Crosslinked Vesicles by Co‐Self‐Assembly of a Gelable Diblock Copolymer and Mercaptosilane

Herein, a convenient and general method to simultaneously fix and functionalize polymeric vesicles with sulphydryl groups by the co‐self‐assembly of poly(ethylene oxide)‐block‐poly[3‐(triethoxysilyl)propyl methacrylate] (PEO‐b‐PTESPMA) and 3‐mercaptopropyltrialkoxysilane in an aqueous solution is reported. The presence of sulphydryl groups across the vesicle membrane has been confirmed by using an energy‐filtered technique during TEM analysis and by capturing Au nanoparticles.

     

From Nanodot to Nanowire: Hybrid Au/Titania Nanoarrays by Block Copolymer Templates

A simple scheme to fabricate 2‐D arrays of Au/titania hybrid nanopatterns is presented, using polystyrene‐block‐poly(ethylene oxide) diblock copolymer (PS‐b‐PEO) as templates coupled with sol–gel chemistry. Both the functionalized Au nanoparticles (NPs) and titania precursors are selectively incorporated into the PEO domain. A series of morphologies ranging from nanodot to nanowire arrays is formed and the mechanism of morphological evolution is discussed. Such hybrid films exhibit characteristic localized surface plasmon resonance bands originating from the coupling between neighboring Au NPs spatially located in a controlled manner.

     

Highly Asymmetric Phase Diagram of a Poly(1,2‐octylene oxide)–Poly(ethylene oxide) Diblock Copolymer System Comprising a Brush‐Like Poly(1,2‐octylene oxide) Block

The phase diagram of a series of poly(1,2‐octylene oxide)–poly(ethylene oxide) (POO–PEO) diblock copolymers is determined by small‐angle X‐ray scattering. The Flory–Huggins interaction parameter was measured by small‐angle neutron scattering. The phase diagram is highly asymmetric due to large conformational asymmetry that results from the hexyl side chains in the POO block. Non‐lamellar phases (hexagonal and gyroid) are observed near f_PEO = 0.5, and the lamellar phase is observed for f_PEO ≥ 0.5.

     

Combining Steric and Electrostatic Stabilization Using Hydrophilic MacroRAFT Agents in an Ab Initio Emulsion Polymerization of Styrene

Hydrophilic (co)polymers carrying a thiocarbonyl thio end group such as poly(dimethylaminoethyl methacrylate), poly(ethylene oxide), and poly(ethylene oxide)‐block‐poly(dimethylaminoethyl methacrylate) have been evaluated as precursors of stabilizers in batch ab initio emulsion polymerization of styrene under acidic conditions to form electrosterically stabilized polystyrene latex particles. As a mixture of P(DMAEMA/H⁺Cl⁻)‐RAFT and PEO‐RAFT failed to give satisfactory results, PEO‐RAFT was used as a control agent for the RAFT polymerization of DMAEMA, and the resulting block copolymer was successfully used in ab initio styrene emulsion polymerization.

     

Novel Structured Composites Formed from Gold Nanoparticles and Diblock Copolymers

We report a simple procedure to prepare a novel Au‐micelle composite with a core‐shell‐corona structure. This composite is prepared by reduction of tetrachloroauric acid (HAuCl₄ · 3H₂O) in dilute aqueous solution containing polystyrene‐block‐poly(4‐vinylpyridine) micelles and poly(ethylene oxide)‐block‐poly(4‐vinylpyridine) copolymers. The micelles with a polystyrene core and a poly(4‐vinylpyridine) shell are transformed into Au‐micelle composites with a polystyrene core, a swollen hybrid Au/poly(4‐vinylpyridine) inner shell, and a poly(ethylene oxide) corona by direct physisorption of gold particles with poly(4‐vinylpyridine) chains.

     

Microphase‐Separated Brushes on Square Platelets in PS‐b‐PEO Thin Films

In polystyrene‐block‐poly(ethylene oxide) thin films, microphase‐separated brushes on the square platelets can be obtained via fast solvent evaporation by controlling the tethering density (0.08 < σ < 0.11). The tethering density of the brushes is proportional to the thickness of the PEO crystal and increases with increasing initial solution heating temperature (T_i). When T_i < T_m, where T_m is the melting point of PEO, brushes with microphase‐separated structures are observed. The formation of microphase‐separated brushes depends on two factors: the strong incompatibility between PS and noncrystalline PEO chains (attached to the crystalline PEO) and the weak interaction between PS‐PS brushes.