Palladium‐Catalyzed Phosphonation of Polyphenylsulfone

An efficient synthetic procedure for the phosphonation of aromatic polymers was developed and is here exemplified for polyphenylsulfone. This procedure involved the bromination of the polymer and the subsequent bromine‐phosphorus exchange by means of a Pd(0)‐catalyzed P? C coupling reaction. In the resulting product, the phosphonate ester pendant groups were attached to aromatic rings of the polymer chain without alkylene spacer units. A substitution degree of almost one phosphonate moiety per repeating unit of the polymer was achieved in the presence of Pd₂(dba)₃ · CHCl₃ as catalyst at 120 °C. Polymers with free phosphonic acid groups were prepared by ester hydrolysis.

     

Allyl End‐Functionalized Poly(ethylene oxide)‐block‐poly(methylidene malonate 2.1.2) Block Copolymers: Synthesis,Characterization, and Chemical Modification

Summary: Poly(ethylene oxide)‐block‐poly(methylidene malonate 2.1.2) block copolymer (PEO‐b‐PMM 2.1.2) bearing an allyl moiety at the poly(ethylene oxide) chain end was synthesized by sequential anionic polymerization of ethylene oxide (EO) and methylidene malonate 2.1.2 (MM 2.1.2). This allyl functional group was subsequently modified by reaction with thiol‐bearing functional groups to generate carboxyl and amino functionalized biodegradable block copolymers. These end‐group reactions, performed in good yields both in organic media and in aqueous micellar solutions, lead to functionalized PEO‐b‐PMM 2.1.2 copolymers which are of interest for cell targeting purposes.

Synthetic route to α‐allyl functionalized PEO‐b‐PMM 2.1.2 copolymers.     

Peroxide‐Grafted PDMS: Hydrosilylation Reaction and Thiol‐Ene Chemistry as an Alternative Pathway

Peroxide‐containing PDMS was synthesized according to a new pathway. Although hydrosilylation is one of the main reactions carried out in silicone chemistry, the catalysts used are very sensitive to the chemical nature of the reactants and remained inefficient to graft allylic peroxide. Radical catalyzed thiol‐ene chemistry was involved for the first time to yield an initiator group containing polymer. The peroxide‐grafted polysiloxane structure and decomposition were characterized using ¹H, ¹³C and ²⁹Si NMR, FT‐IR and Raman spectroscopies, SEC and DSC. These macroinitiators can be used to obtain polysiloxane able to undergo crosslinking.

     

Tailoring Linear and Nonlinear Optical Properties of a Side‐Chain Liquid Crystalline Azo‐Polymethacrylate

The molecular orientation in a side‐chain liquid crystalline azopolymer with push–pull chromophores ( Pol‐PZ‐CN ) is studied by UV‐vis spectroscopy, refractive index and second harmonic generation measurements. Fresh films show homeotropic arrangement, but irradiation with polarized light induces “in‐plane” birefringence, which is enhanced by subsequent thermal annealing up to values as high as 0.34. The nonlinear response of Corona poled films with “in‐plane” anisotropy is governed by three independent NLO d_ij coefficients, evidencing symmetry different from the usual (C_∞v). For irradiated films, stable values d₃₁ = 1.4, d₃₂ = 0.9 and d₃₃ = 11 pm·V^?1 are measured at 1.9 µm. A noticeable higher d₃₁/d₃₂ ratio is obtained for preirradiated and annealed films. The proposed two‐step method consisting of light irradiation and heating is an effective strategy to tailor the polar molecular orientation of nonlinear liquid crystalline azopolymers.

     

Synthesis and self‐assembly of polymers containing dicarboximide groups by living ring‐opening metathesis polymerization

Polymers with narrow molecular weight distributions and controlled architectures were generated by living ring‐opening metathesis polymerization of exo‐7‐oxabicyclo[2.2.1]hept‐5‐ene‐2,3‐dicarboximide. The dicarboximide units have been previously shown to exhibit biological activity, can selectively bind to the nucleic acid base adenine by hydrogen‐bonding, and are readily functionalizable. Block copolymers containing these moieties were generated, and underwent self‐assembly into nanoscale spherical aggregates, with surface localized molecular recognition motifs.

     

A Facile One‐Pot Synthesis to Dextran‐Based Nanoparticles with Carboxy Functional Groups

Summary: Stabilized nanoparticles functionalized with carboxy groups were synthesized directly from dextran and acrylic acid (AA), without using any organic solvent and surfactant. The composition and morphology of these dextran‐based nanoparticles, as well as the mechanism of this one‐pot synthesis, were also investigated in this paper. This approach is anticipated to be applicable to various water‐soluble polysaccharides to fabricate nanoparticles facilely.

Facile synthesis of stabilized nanoparticles functionalized with carboxy groups from dextran and AA.     

New Star‐Branched Poly(acrylonitrile) Architectures: ATRP Synthesis and Solution Properties

Summary: Atom transfer radical polymerization (ATRP) has been chosen as “living”/controlled free radical polymerization system to synthesize a number of novel poly(acrylonitrile) (PAN) architectures. The reaction conditions for the synthesis of linear samples with control over molar mass and molar mass distribution have been investigated together with the possibility of obtaining copolymers of acrylonitrile with small quantities of methyl acrylate (max. 5 mol‐%). Well‐defined star polymers with 3, 4 and 6 arms have been successfully synthesized together with linear chains initiated by a bifunctional initiator and star‐branched polymers with a hyperbranched poly(ester amide) as core. Molar masses were determined by NMR and GPC with the latter leading to a significant over estimation. Solution viscosity studies indicated that the stiff structure of the PAN chains is still maintained in the homopolymer star architectures and that the incorporation of small quantities of methyl acrylate as comonomer has a stronger effect on chain flexibility than the incorporation of star‐branch points.

     

High‐Performance Polybenzoxazine Nanocomposites Containing Multifunctional POSS Cores Presenting Vinyl‐Terminated Benzoxazine Groups

We have prepared a new class of polybenzoxazine/POSS nanocomposites through the reactions of a multifunctional vinyl‐terminated VBa‐POSS with a VBa monomer at various compositional ratios. The incorporation of the silsesquioxane core units into the polybenzoxazine matrix significantly hindered the mobility of the polymer chains and enhanced the thermal stability of these hybrid materials. Increasing the POSS content in these hybrids improved their thermal and mechanical properties, relative to those of the neat polybenzoxazine, because of hydrogen bonding between the siloxane groups of the POSS core units and the OH groups of the polybenzoxazine moieties, as adjudged using FTIR spectroscopy.

     

Synthesis,Characterization, and Thermal Properties of Block Copolymers Containing Poly(styrene‐co‐4‐vinylpyridine) and Poly(styrene‐co‐butyl acrylate) by Controlled Radical Polymerization

Radical polymerization of styrene and mixtures of styrene and 4‐vinylpyridine was performed in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) producing polymers with controlled molecular weights and molecular weight distributions. The living nature of these polymers was confirmed by using them as macroinitiators in the block copolymerization of styrene and butyl acrylate. The thermal properties of the synthesized statistical diblock copolymers measured by differential scanning calorimetry indicated that a phase‐separated morphology was exhibited in most of the block copolymers. The results were confirmed by transmission electron microscopy (TEM) and small angle X‐ray scattering (SAXS) showing microphase‐separated morphology as is known for homo A‐B diblock polymers.

SAXS of a block copolymer synthesized from S/V 70:30 macroinitiators (03) with one detected T_g.     

Nickel‐Mediated Surface Grafting From Polymerization of α‐Amino Acid‐N‐Carboxyanhydrides

Summary: The feasibility of a living grafting from polymerization of α‐amino acid‐N‐carboxyanhydrides (NCA) from a surface using nickel initiators was shown. The polymerization has been carried out on commercially available polystyrene resins as spherical substrates in two different ways. Firstly L ‐glutamic acid was bound to the surface as γ‐ester via a UV‐labile linker and transferred into the NCA by treatment with triphosgene. The grafting from polymerization was then carried out as a “block copolymerization” by reaction of the surface bound NCA with an excess of the Ni amido‐amidate complex initiator and subsequent addition of free NCA to grow the polymer chain. By this procedure polymer was formed at the surface and can be isolated after photolysis of the linker. The characterization of the polymer by size exclusion chromatography indicates a living polymerization at the surface. The second approach employs N‐alloc‐amides at the surface to prepare an initiating Ni amido‐amidate complex directly at the surface. It can be shown that the latter approach is much more straightforward and gives smaller quantities of non‐tethered polypeptide.

Surface bound polypeptides were obtained by ring opening polymerization of α‐amino acid‐N‐carboxyanhydrides initiated by nickel amido‐amidate complexes installed at surfaces of commercially available polystyrene resins.     

Electrochemical Surface Plasmon Resonance and Field‐Enhanced Light Scattering: Monomer Copolymerization with a Polysiloxane‐Conjugated Polythiophene Network Precursor

The in situ electrochemical and dielectric film properties of monomer co‐electropolymerization with a CPN precursor was investigated. A polysiloxane/polythiophene precursor was electropolymerized with thiophene monomer at different composition ratios using cyclic voltammetry. This was investigated in situ by EC‐SPR spectroscopy and EC‐SPFELS. The characteristic oscillations corresponded to distinct transitions in film deposition. The resonance coupling of the SPR decreased with higher thiophene monomer content. Increasing the amount of thiophene monomer increased the RMS roughness of the film as observed by AFM, which corresponded to an increase in scattered light intensity with EC‐SPFELS.

     

Low‐Temperature Polymerization of Olefins in the Presence of Titanium Monoamidinate/MAO Catalyst

This paper reports the predominantly syndiotactic‐specific polymerization of propylene in the presence of titanium monoamidinate/methylaluminoxane (MAO) catalysts. The same catalysts, depending on the reaction conditions, also promote either predominantly 1,4‐cis or 1,4‐trans polymerization of 1,3‐butadiene and polymerization of styrene either to highly syndiotactic or to stereoirregular polymer. Some preliminary information about the features of propylene polyinsertion is also reported.

Expansion of the 20–24 ppm region of the ¹³C NMR spectrum of sample 2. The starred resonance at 21.75 ppm and the shoulders are not assigned.     

An Easy Strategy for the Synthesis of Well‐Defined Aliphatic‐Aromatic Hyperbranched Polyesters

A one‐pot solution polymerization under mild conditions was adapted for the synthesis of well‐defined aliphatic‐aromatic polyesters with different degrees of branching. The esterification was performed at room temperature using 4,4‐bis(4′‐hydroxyphenyl)valeric acid (AB₂) and 3‐(4‐hydroxyphenyl)propionic acid (AB) as monomers. DPTS was used as a catalyst and DCC as a coupling agent. Polyesters with statistical, dendritic topology, controlled degree of branching and > 35 000 g · mol^?1 were obtained. The polymers were characterized by ¹H and ¹³C NMR, SEC, DSC, and TGA. A strong dependence of the degree of branching and the thermal properties of the polymers depending on the AB/AB₂ monomer ratio was observed.

     

Fluorinated Styrene‐ and Carbazole‐Based Cladding Polymer Layers for EO and NLO Polymer Devices

Novel polymer cladding materials were synthesized and their potential for use in optical waveguide devices was investigated. 9‐[2‐(2,3,5,6‐Tetrafluoro‐4‐vinylphenoxy)ethyl]‐9H‐carbazole and 1‐pentafluorophenylpyrrole‐2,5‐dione were used as comonomers for preparing the acrylic cladding copolymers. These showed a low resistivity (≈2 × 10¹³ Ω · cm) at room temperature and a low optical loss (?0.6 dB · cm^?1) at a wavelength of 1.55 µm. The refractive indexes and the glass transition temperatures of the polymer cladding materials can be controlled by the composition of the copolymers. The resulting polymers are good candidates for cladding materials for practical applications in devices.

     

The Process of Functional Conjugated Organic Polymers Derived from Triple‐Bond Building Blocks

Polyacetylenes, poly(p‐phenyleneethynylenes), and polydiacetylenes, as conjugated polymers derived from triple‐bond containing building blocks, attain considerable attention because of their electronic and photoconduction properties. In this review, recent studies on the design and synthesis of conjugated polymers derived from triple‐bond building blocks are summarized with an emphasis on the developments in our group in recent years. Our intense attention is focused on constructing different molecular systems with enhanced light‐harvesting efficiency, and determining the functional properties of conjugated organic polymers. The conjugated organic polymers that appear in this review are useful candidates for various potential applications because of their extraordinary optical and electronic properties. The potential applications of the conjugated polymer‐containing systems are explored.

     

Functional Beads of Polyvinylpyrrolidone: Promising Support Materials for Solid‐Phase Synthesis

Summary: The solubility properties of polyvinylpyrrolidone (PVP) make it an attractive material for several different polymer‐assisted synthesis applications. However, PVP lacks reactive groups necessary for attaching compounds to the polymer. Furthermore, the radical reactivity of 1‐vinylpyrrolidin‐2‐one (NVP) is different from most other monomers, which results in compositional drift during copolymerization. Therefore, introducing reactive groups into the polymer using this method is intricate. Smaller differences in radical reactivity are expected from monomers that are derivatives of NVP itself. Hence, such monomers provide a way of preparing PVP with adjustable properties. Four new monomers containing pendant double bonds, all derivatives of NVP, were synthesized and used in the preparation of a new type of hydrophilic polymer bead by aqueous suspension polymerization. We also found that undec‐10‐en‐1‐ol can be used as a comonomer for the introduction of functional groups. The lightly crosslinked beads contain hydroxyl groups at a functional loading of 0.28 mmol/g and swell extensively in a broad range of solvents. Their potential as support materials has previously been demonstrated in a five‐step solid‐phase synthesis of 5‐(2,4,6‐trimethoxy‐phenyl)‐cyclohexa‐1,3‐dienecarboxylic acid.

Scanning electron microscopy image of dry beads from PVP‐[B]₂.     

Synthesis and Study of CdS Nanoparticle‐Doped Poly(1,4‐dihexyloxybenzene)

A simple, economical and high yielding method to prepare poly(1,4‐dihexyloxybenzene), an alkylated derivative of poly(para‐phenylene) (PPP), is reported. We further prepared a composite of poly(1,4‐dihexyloxybenzene) and CdS nanoparticles and studied their structural, optical, stability and transport properties. It was observed that the conductivity of poly(1,4‐dihexyloxybenzene) increased by several orders of magnitude when doped with CdS nanoparticles. Similarly, CdS nanoparticle‐doped PPP showed higher thermal stability, when compared to the neat polymer. As these composites could be processed in the same way as organic polymers, they would find applications in many low‐cost optoelectronic devices.

     

Preparation and Characterisation of Hydrophobically Modified Hydroxypropylcellulose: Side‐Chain Crystallisation

Summary: Hydroxypropylcellulose has been hydrophobically modified by reaction with different amounts of palmitoyl chloride. When the degree of substitution is sufficiently high, the side chains are able to produce lateral crystallisation, which has been analysed by DSC and diffraction experiments, using both conventional and synchrotron radiation. The melting temperatures and enthalpies depend on the degree of substitution, in such a way that it is relatively easy to get melting temperatures close to that of the human body, although a rather wide melting region is obtained.

X‐ray diffractograms of the original HPC sample and of the modified specimens.     

Semicontinuous Emulsion Polymerization of Butyl Methacrylate and 1, 3‐Butadiene in the Presence of Cyclodextrins and Cytocompatibility of Dicarboxylic Acid Telechelic Oligo(butyl Methacrylate)s Derived from Ozonolysis of the Latexes

Ozonolysis of unsaturated polymers produced useful telechelic oligomers that can form building blocks for networks and block copolymers. The unsaturated polymers can be prepared by semicontinuous emulsion polymerization with dienes, and here it is shown that the addition of cyclodextrins enhanced the incorporation of these comonomers. Both α‐ and β‐cyclodextrin provide copolymers with higher fractions of butadiene (BD) incorporated into the chain but α‐cyclodextrin had the highest levels of incorporation. Oxidative work up after ozonolysis produced latexes of carboxylic acid oligomers of different molar masses. A clear effect of polymer size on toxicity was observed with the oligomers with < 2 700 g · mol.^?1 proving to have similar cytotoxic effects to lactic acid. However, oligomers with above 2 700 g · mol.^?1 were cytocompatible and gave similar results to a polylactide control material.

     

Modification of Polyethylene by VUV Irradiation in the Presence of Trimethylsilane and Oxygen

The photoassisted modification of LDPE by VUV irradiation in a reactive trimethylsilane/oxygen atmosphere was investigated. The modified LDPE surface was investigated by FT‐IR, XPS, contact‐angle measurements and electron microscopy. Attachment of alkylsilyl and Si–O units to LDPE was observed. Best results were obtained using an equimolar trimethylsilane/oxygen mixture. Low‐energy surfaces were obtained after a few minutes of irradiation at an intensity of 1.7 mW · cm^?2. After prolonged irradiation, the thickness of the modified polyethylene layer is approximately 700 nm. Surface modifications of this type may be of interest to obtain protective and barrier layers on polyolefins.