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.

     

Towards the Generation of Self‐Healing Materials by Means of a Reversible Photo‐induced Approach

Photo‐induced reversibility as a tool for self‐healing: a reversible photo‐induced dendritic macromonomer was synthesized and proven to form networks with different features depending on the crosslinking conditions. While networks formed from aqueous systems exhibited a reversible change in their crosslinking degree, networks generated in bulk underwent fully reversibility. The latter was then exploited for generating self‐healing materials by means of a photo‐induced treatment.

     

Tools to Simulate Distributive Mixing in Twin‐Screw Extruders

The application of the mapping method in finite element modeling is extended to quantitatively compare mixing in different twin‐screw extruder layouts. The mapping method provides volumetric quantities, which are crucial for the analysis and optimization of mixing based on the tracking of particles in the velocity field. A new approach to the mapping method is developed to analyze mixing in complex, dynamic open geometries. Several screw configurations and different types of conveying screws are compared, changing the pitch and gap widths. The volume‐weighted intensity of segregation is used as a mixing measure.

     

pH Responsive Polymeric Brush Nanostructures: Preparation and Characterization by Scanning Probe Oxidation and Surface Initiated Polymerization

pH‐responsive PHEMA‐based polymeric nanostructures were grown in a controlled manner by ATRP‐based surface‐initiated polymerization. Initiator nanopatterns were obtained on silicon wafers covered with OTS resists made by AFM scanning probe oxidation lithography. AFM images confirmed isolated grafting of stimuli‐responsive hedge and dot brush structures exhibiting dimensions corresponding to a few tens of chains.

     

Optically Triggered Dissociation of Kinetically Stabilized Block Copolymer Vesicles in Aqueous Solution

We demonstrate a strategy for using an optical stimulus to trigger the dissociation of block copolymer (BCP) vesicles in aqueous solution. The BCP, comprising hydrophilic poly(ethylene oxide) (PEO) and a block of poly(methacrylic acid) bearing a number of spiropyran methacrylate comonomer units (P(MAA‐co‐SPMA)), was allowed to firstly self‐assemble into large vesicles in aqueous solution at pH = 3 with protonated carboxylic acid groups, and then become kinetically stable at pH = 8 due to the glassy vesicle membrane of P(MAA‐co‐SPMA). Fast dissociation of the vesicles was achieved through a cascade of events triggered by UV‐induced isomerization from neutral spiropyran to charged merocyanine in the membrane.

     

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.

     

Chain Transfer and Efficiency of End‐Group Introduction in Free Radical Polymerization of Methyl Methacrylate in the Presence of Poly(methyl methacrylate) Macromonomer

Summary: Experimental and modeling studies of addition–fragmentation chain transfer (AFCT) during radical polymerization of methyl methacrylate in the presence of poly(methyl methacrylate) macromonomer with 2‐carbomethoxy‐2‐propenyl ω‐ends (PMMA‐CO₂Me) at 60 °C are reported. The results revealed that AFCT involving PMMA‐CO₂Me formed in situ during methyl methacrylate polymerization has a negligible effect on the molecular weight distribution.

     

Polymer‐Based Rectifying Diodes on a Glass Substrate Fabricated by Ink‐Jet Printing

Summary: The fabrication of polymer diodes on a glass substrate by an ink‐jet printing technique is reported. Both an n‐type semiconductive polymer, poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐(1‐cyanovinylene)phenylene] (CN‐PPV), and a p‐type semiconductive polymer, polypyrrole (PPy) or poly(3,4‐ethylenedioxythiophene) (PEDOT), were printed through a piezoelectric ink‐jet printer. The printed CN‐PPV/PPy and CN‐PPV/PEDOT diodes showed good rectifying characteristics. These results indicate the potential of the low‐cost ink‐jet printing technique to produce polymer microelectronic devices and circuits.

Schematic diagram of the printed polymer diode     

Mapping Acid‐Catalyzed Deprotection in Thin Polymer Films: Fluorescence Imaging Using Prefluorescent 7‐Hydroxycoumarin Probes

Summary: Fluorescent images that illustrate acid‐catalyzed tert‐butoxycarbonyl (tBoc) deprotection patterns in polymer films were obtained using fluorescent sensors based on 7‐hydroxycoumarin dyes. Three commercial 7‐hydroxycoumarins, which are highly fluorescent, become practically nonemissive upon protection of the 7‐hydroxyl position with tBoc. In thin polymer films, the protected “prefluorescent” probes can return to their deprotected, fluorescent states by reaction with catalytic amounts of photogenerated acid and mild heating.

Protected probes become highly fluorescent after acid‐induced deprotection.     

Facile Access to Hydroxy‐Functional Core–Shell Microspheres via Grafting of Ethylene Oxide by Anionic Ring‐Opening Polymerization

We present a facile access route to hydroxy‐functional narrow disperse microspheres of well‐defined grafting density (GD). Ethylene oxide has been grafted from highly crosslinked poly(divinyl benzene) microspheres by anionic ring‐opening polymerization using sec‐butyllithium as activator together with the phosphazene base t‐BuP₄. Initially, core microspheres have been prepared by precipitation polymerization utilizing divinyl benzene (DVB, 80 wt.‐%). The grafting of poly(ethylene oxide) (PEO) from the surface resulted in the formation of functional core–shell microspheres with hydroxy‐terminal end groups. The number average particle diameter of the grafted microspheres was 3.6 µm and the particle weight increased by 5.7%. The microspheres were characterized by SEM, FT‐IR spectroscopy, elemental analysis, and fluorescence microscopy. The surface GD (determined via two methods) was 1.65 ± 0.06 and 2.09 ± 0.08 chains · nm⁻², respectively.

     

Dendritic Carrier Based on PEG: Design and Degradation of Acid‐sensitive Dendrimer‐like Poly(ethylene oxide)s

Degradable dendrimer‐like PEOs were designed using an original ABC‐type branching agent featuring a cleavable ketal group, following an iterative divergent approach based on the anionic ring opening polymerization (AROP) of ethylene oxide and arborization of PEO chain ends. A seventh generation dendrimer‐like PEO carrying 192 peripheral hydroxyls and exhibiting a molar mass of 446 kg · mol⁻¹ was obtained in this way. The chemical degradation of these dendritic scaffolds was next successfully accomplished under acidic conditions, forming linear PEO chains of low molar mass (≈2 kg · mol⁻¹), as monitored by ¹H NMR, SEC, and MALDI‐TOF mass spectrometry as well as by AFM.

     

Hyperbranched Polycarbonate‐Based Multimolecular Micelle with Enhanced Stability and Loading Efficiency

We herein develop a facile catalyst‐free method to prepare hyperbranched hydroxyl‐enriched aliphatic polycarbonate according to SCROP strategy. PEG‐attached multiarm hyperbranched copolymer HEHDO‐star‐mPEG was further designed. It was found that HEHDO‐star‐mPEG can self‐assemble into supramolecular multimolecular micelles in water. HEHDO‐star‐mPEG micelle showed excellent stability with respect to micellar size upon dilution, and displayed good cell‐biocompatibility. An anticancer drug of doxorubicin with hydrogen‐bonding functionality was incorporated into obtained micelles to establish a drug delivery system model. A high drug‐loading content as well as sustained release pattern for HEHDO‐star‐mPEG based delivery system was achieved.

     

Controlling Fusion and Aggregation in Polymersome Dispersions

The effects of addition of poly(ethylene oxide) (PEO) to poly(ethylene oxide)₁₆‐block‐poly(butylene oxide)₂₂ (EB1) polymersome dispersions has been studied. Aggregation and membrane fusion between polymersomes were observed with great control of the outcome by varying PEO molecular weight. Small‐scale fusion of 2 to 3 polymersomes was seen with low‐molecular‐weight PEO, whilst large‐scale aggregation occurred above a critical PEO molecular weight of 4 000 Da. The resulting highly porous EB1‐PEO aggregate shows great promise for applications in cell entrapment for transport and delivery, and as a three‐dimensional scaffold for use in tissue engineering.

     

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.     

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.     

Block Copolymer PEO‐b‐PHPMA Synthesis Using Controlled Radical Polymerization on a Chip

Summary: Block copolymers of poly(ethylene oxide‐block‐2‐hydroxypropyl methacrylate) (PEO‐b‐PHPMA) with a range of molecular masses of the PHPMA block were obtained by controlled radical polymerization on a chip (CRP chip) using a PEO macroinitiator. A series of well‐controlled polymerizations were carried out at different pumping rates or reaction times with a constant ratio of monomer to initiator. The stoichiometry of the reactants was also adjusted by varying relative flow rates to change the reactant concentrations.

A schematic of a CRP chip and SEC traces of the PEO‐b‐PHPMA produced from different pump rates with a 1:100 ratio of initiator to monomer. The dashed peaks are the macroinitiator, PEO‐Br (left), and monomer, HPMA (right).     

Poly(ethylene oxide) hydrogels as semi-permeable membranes for an artificial pancreas

Poly(ethylene oxide) (PEO) hydrogels were synthesized in organic solvents, or for better results in water, via the free-radical homopolymerization of α,ω-methacryl-oyloxy PEO macromonomers. Their characteristics (amount of extractable material, equilibrium swelling degree, uniaxial compression modulus) could be controlled by the polymerization parameters (precursor molar mass, macromonomer concentration, polymerization time). In aqueous media, the hydrophobic end-standing polymerizable methacrylic units of the macromonomers self-organize, and their polymerization leads to networks with better mechanical properties than those prepared with the same macromonomers but in organic solvents. In vitro tests confirmed their good biocompatibility: almost no adhesion of cells was evident. It was confirmed that glucose diffuses through these hydrogels. Insulin diffusion was also studied but found to be more complex.

Schematic representation of a device for an artifical pancreas based on a vascular system.     

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.

     

Transparent and Conductive Polyethylene Oxide Film by the Introduction of Individualized Single‐Walled Carbon Nanotubes

It is demonstrated that an optically transparent and electrically conductive polyethylene oxide (PEO) film is fabricated by the introduction of individualized single‐walled carbon nanotubes (SWNTs). The incorporated SWNTs in the PEO film sustain their intrinsic electronic and optical properties and, in addition, the intrinsic properties of the polymer matrix are retained. The individualized SWNTs with smaller diameter provide high transmittance as well as good electrical conductivity in PEO films.

     

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.