Linear Terpyridine‐Ruthenium(II) Poly(ethylene glycol) Coordination Polymers

In the present contribution, we synthesized linear coordination polymers based on oligo(ethylene glycol)s as well as poly(ethylene glycol)s and terpyridine ruthenium(II) complexes. The reaction conditions, e.g., solvent, concentration, were varied to obtain well‐soluble, high molecular weight polymers. The resulting compounds were characterized by UV‐vis and NMR spectroscopy. The viscosity of the materials was also investigated with and without salt addition. Finally, the polymers were characterized with DSC and AFM. AFM revealed a lamellar morphology.

     

Controlled Synthesis of Well Defined Poly(3‐hydroxyalkanoate)s‐based Amphiphilic Diblock Copolymers Using Click Chemistry

A modular synthesis of short chain length and medium chain length poly(3‐hydroxyalkanoate)s‐b‐poly(ethylene glycol) (PHAs‐b‐PEG) diblock copolymers is described. First, length‐controlled oligomers of hydrophobic poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBHV), poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHHx), and poly(3‐hydroxyoctanoate‐co‐hydroxyhexanoate) (PHOHHx) containing a carboxylic acid end group were obtained by thermal treatment, with molar masses ranging from 3 800 to 15 000 g · mol^?1. After quantitative functionalization with propargylamine, ligation with azide‐terminated poly(ethylene glycol) of 5 000 g · mol^?1 was accomplished using the copper (I) catalyzed azide alkyne cycloaddition (CuAAC). Well‐defined diblock copolymers were obtained up to 93% yield, with molar masses ranging from 9 900 to 23 100 g · mol^?1. All products were fully characterized using ¹H NMR, COSY, SEC, TGA, and DSC.

     

Enhanced,Perpendicular Liquid‐Crystal Alignment on Rubbed Films of a Coumarin‐Containing Polystyrene

We synthesized a series of polystyrene derivatives containing coumarin side groups using polymer analogous reactions. The liquid‐crystal (LC) alignment director for these polymer films was found to be perpendicular to the rubbing direction. The contrast ratio and anchoring‐energy values of these polystyrene derivatives were found to be much greater than those of polystyrene and poly(chloromethylstyrene), indicating that the coumarin side groups increase the aligning ability. For example, the anchoring energy of a polymer with 82 mol‐% of coumarin‐containing monomeric units, compared to polystyrene, is about 7 × 10^?5 J · m^?2 and 1 × 10^?7 J · m^?2, respectively.

     

Stereocomplex Formation in Polylactide Multiarm Stars and Comb Copolymers with Linear and Hyperbranched Multifunctional PEG

A systematic comparison between graft poly(l‐ lactide) copolymers with different topologies and their ability to form stereocomplexes with poly(D ‐lactide) (PDLA) is performed. Comb and hyperbranched copolymers based on functional poly(ethylene glycol) and poly(l‐ lactide) with molecular weights in the range of 2000–90 000 g mol^?1 and moderate molecular weight distributions (M _w/M _n = 1.08–1.37) are prepared via the combination of anionic and ring‐opening polymerization. Two “topological isomers,” a linear poly(ethylene oxide)/poly(glycerol) (PEG/PG) copolymer and a branched PEG/PG copolymer are used as backbone polymers. Furthermore, the stereocomplex formation between PDLA and the hyperbranched and comb copolymers containing poly(l‐ lactide) arms is studied. Stereocomplex formation is confirmed by DSC as well as by Fourier transform IR (FTIR) and Raman spectroscopy.

     

Synthesis of Polyphenylene Ether Derivatives: Estimation of Their Dielectric Constants

A series of poly(2‐alkyl‐6‐phenylphenylene ether)s were prepared by the oxidative polymerization of 2‐alkyl‐6‐phenylphenols. Their dielectric constants were approximately 2.5, whereas it was found that the phenyl group at the 6‐position clearly increased the Q factor of the polymer compared with poly(2,6‐dimethylphenylene ether), PPE. These values were qualitatively predicted from the polarizability and the molar volume calculated by the theoretical analysis of the unit structure at the HF/6‐31G* level.

     

Preparation of Crosslinked Poly(2‐bromoethyl methacrylate) Microspheres and Decoration of Their Surfaces with Functional Polymer Brushes

Synthesis and crosslinking copolymerization of 2‐bromoethylmethacrylate in aqueous suspension is described for preparing bromoalkyl‐functional microbeads (125–420 µm). Highly transparent microspheres with a density of accessible bromoethyl groups of 1.55 mmol · g^?1 were prepared in the suspension, stabilized with poly(N‐vinyl pyrrolidone), by using methyl methacrylate as diluting co‐monomer and ethylene glycol dimethacrylate as crosslinker. Bromoalkyl groups on the microparticles were employed as initiation sites for either surface‐initiated ATRP of glycidyl methacrylate or ring‐opening polymerization of 2‐methyl‐2‐oxazoline to generate epoxy‐ and N‐acetylethyleneimine‐functional hairy grafts, tethered to the particle surfaces with hydrolytically stable linkages.

     

Synthesis and Characterization of Block Copolymers of ε‐Caprolactone and DL‐Lactide Initiated by Ethylene Glycol or Poly(ethylene glycol)

Biodegradable copolymers were prepared by ring‐opening polymerization of sequentially added ε‐caprolactone and DL ‐lactide in the presence of ethylene glycol or poly(ethylene glycol), using zinc metal as catalyst. Polymerization was performed in bulk and yielded block copolymers with predetermined PEG/PCL/PLA segments. The obtained polymers were characterized by ¹H NMR, SEC, IR, DSC, TGA, and X‐ray diffraction. Data showed that the copolymers preserved the excellent thermal behavior inherent to PCL. The crystallinity of PLA‐containing copolymers was reduced with respect to PCL homopolymer. The presence of both hydrophilic PEG and fast degrading PLA blocks should improve the biocompatibility and biodegradability of the materials, which are of interest for applications as substrate in drug delivery or as scaffolding in tissue engineering.

Block copolymerization of ε‐caprolactone and DL ‐lactide initiated by dihydroxyl PEG.     

Luminescent Polymeric Dispersions and Films Based on Oligonuclear Lanthanide Clusters

The successful embedding of different amounts and types of hydrophobic rare earth clusters (Ln = Y, Pr, Eu, Sm, Nd) in various polymer matrices via miniemulsion polymerization is presented. The resulting cluster‐polymer hybrid nanoparticles are spherical in shape and possess a narrow size distribution, as investigated by photon cross correlation spectroscopy (PCCS) and transmission electron microscopy (TEM). The exact Ln‐content in the nanoparticles is exemplarily investigated for Eu‐ and Nd‐containing polymer dispersions via inductively coupled plasma‐optical emission spectrometry (ICP‐OES). As a result of encapsulation more than 1000 mg · L^?1 of the hydrophobic Ln‐cluster are successfully dispersed in water. The photophysical properties of the emulsion show the successful avoidance of water from the vicinity of the clusters. Furthermore, a very efficient energy transfer from the ligand and polymeric unit to Eu³⁺ ions can be observed in dispersion. Based on the different glass transition temperatures (T_g) of the applied polymers, monolayers of the nanoparticles and efficient luminescent thin polymer films are obtained by spin coating.

     

Synthesis of Well‐Defined Hybrid Macromonomers of Poly(ethylene oxide) and Their Reactivity in Photoinitiated Polymerization

Summary: α,ω‐Hybrid (hetero‐telechelic) poly(ethylene oxide) (PEO) macromonomers carrying both cationic and radical or anionic polymerizable vinyl end groups were newly synthesized by the living anionic polymerization of ethylene oxide (EO) initiated with partially K‐alkoxidated vinylic alcohols such as the monovinyl ether of tetramethylene glycol or di(ethylene glycol) and p‐vinylbenzyl alcohol (VBA), followed by reaction with methacryloyl chloride (MAC). They possess a couple of α‐ and ω‐end groups that can polymerize concurrently or selectively by radical and/or cationic or anionic mechanism. The reactivity of the radical and cationic species formed upon photolysis of benzophenone and triphenylsulfonium tetrafluoroborate towards these end groups were studied by means of ¹H NMR analysis following the disappearance of the respective olefinic groups. Studies with macromomonomers and model compounds revealed that photoexcited benzophenone abstracts hydrogen atoms from the PEO backbone to form radicals without added hydrogen donors. In the case of the sulfonium salt, both radical and cationic species are formed, which react with the respective functional groups. It was also shown that vinyl ether moieties react more readily than the methacrylate in both radical and cationic processes.

The general synthetic strategy followed for the preparation of the hybrid PEO macromonomers studied here.     

Poly(ethylene glycol)‐Coated Magnetite Nanoparticles: Preparation and Characterization

This paper reports a novel synthetic process to obtain poly(ethylene glycol)‐coated magnetite nanoparticles. Magnetite nanoparticles were synthesized by a chemical co‐precipitation of Fe²⁺ and Fe³⁺ ions under alkaline conditions, which were then coated with poly(ethylene glycol) diacrylate via UV‐curing in water. The nanoparticles were characterized by means of DLS, FT‐IR spectroscopy, TGA, TEM, and XPS. The magnetic properties of the magnetic nanoparticles at room temperature were also characterized by the measurement of hysteresis curves using a vibrating‐sample magnetometer.

     

Synthesis of Structurally‐Controlled AIDS Vaccine Model with Glyco‐Peptide Dendrimer Scaffolds

Summary: A novel glyco‐peptide dendrimer‐type AIDS vaccine model with a well‐defined structure was synthesized. A low‐substituted, monodispersed, glyco‐peptide dendrimer was prepared by binding maltose to a proline‐poly(lysine) dendrimer with monofunctional prolyl amino groups on the periphery. To the hemispherical maltose‐proline‐poly(lysine) dendrimer, succinic anhydride was reacted to provide succinylated dendrimer with an average of 13 succinyl carboxyl groups per dendrimer. The reactivity of succinyl‐maltose‐proline‐poly(lysine) dendrimer was investigated by coupling a tripeptide to the carboxyl group in water using 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride (EDC) as a condensing agent. By binding two kinds of peptide sequences included in the envelope glycoprotein of HIV to the dendrimer, AIDS vaccine models with glyco‐peptide dendrimer scaffold were synthesized. The structure of the vaccine models was determined by NMR and MALDI‐TOF mass analyses.

Leu‐Pro‐Gly‐succinyl‐maltose‐proline‐poly(lysine) dendrimer generation 3.     

Synthesis and aqueous phase behavior of thermoresponsive biodegradable poly(D,L‐3‐methylglycolide)‐block‐poly(ethylene glycol)‐block‐poly(D,L‐3‐methylglycolide) triblock copolymers

Novel biodegradable thermosensitive triblock copolymers of poly(D ,L ‐3‐methylglycolide)‐block‐poly(ethylene glycol)‐block‐poly(D ,L ‐3‐methylglycolide) (PMG‐PEG‐PMG) have been synthesized. Ring‐opening polymerization of D ,L ‐3‐methyl‐glycolide (MG) initiated with poly(ethylene glycol) (PEG) and Ca[N(SiMe₃)₂]₂(THF)₂ provided triblock copolymers with alternating lactyl/glycolyl sequences of controlled molecular weight, low polydispersity index and uniform chain structure. At relatively low temperatures (≈ 10 °C) these copolymers formed clear solutions in water up to high concentrations (50 wt.‐%). Depending on molecular mass ratios of PMG and PEG blocks, a sol‐gel transition or an increase in viscosity without gel formation was observed upon increasing the temperature of the aqueous solutions. The temperature‐induced gelation was ascertained by rheology and dynamic differential scanning calorimetry (DDSC).

Phase diagram of PMG‐PEG‐PMG 1 400‐1 450‐1 400 in an aqueous solution.     

Optically Active Poly[{methyl(1‐naphthyl)silylene}(o‐phenylene)methylene]‐Poly(ethylene glycol) Block Copolymer Micelles

Summary: Optically pure (+) and isotactic poly[{methyl(1‐naphthyl)silylene}(o‐phenylene)methylene] terminated with methylphenylchlorosilyl was obtained by the Pt‐catalyzed ring‐opening polymerization of optically pure 1‐methyl‐1‐(1‐naphthyl)‐2,3‐benzosilacyclobut‐2‐ene in the presence of methylphenylchlorosilane as a chain transfer agent. The polymer formed was transformed into a block copolymer by reacting the terminal chlorosilyl group with a commercial poly(ethylene glycol) monomethyl ether. The formation of micelles by the block copolymer in THF‐water mixtures was investigated by fluorescence and UV. More detailed information about the aggregation of the polymer in the micelles was obtained by circular dichroism spectroscopy. It was found that dense aggregates were formed at a concentration higher than the critical micelle concentration. This concentration was higher for lower molecular weight polymer, at higher temperatures, and in more hydrophobic solvent systems. The highly aggregated structure was altered by changing the solvent system.

     

Novel Phosphorous‐Containing Aromatic Polyethers – Synthesis and Characterization

Summary: The synthesis of novel phosphorous‐containing aromatic polyethers P‐PEEK and P‐PSU, based on poly(ether ether ketone)s (PEEK) and poly(ether sulfone)s (PSU) was carried out successfully by using phosphorous‐containing aromatic diols instead of bisphenol A in the usual synthesis procedure. The molecular weights of the P‐PEEKs and P‐PSUs obtained reflect both the influence of the different halogen components used and the lower thermal stabilities of the phosphorous‐containing diols compared to bisphenol A. However, polymers with sufficient molecular weights could be obtained, having interestingly high T_gs, high thermal stabilities as well as modified flame retardance properties depending on the diol type incorporated.

Comparison of the molecular weights of the synthesized P‐polyethers.     

Synthesis of Amorphous Hydrophobic Telechelic Hydrocarbon Diols via ADMET Polymerization

Amorphous, hydrophobic telechelic hydrocarbon diols were synthesized using acyclic diene metathesis (ADMET) polymerization. These diols can be used in hydrolysis and UV resistant polyurethanes. The hydrocarbon backbone is based on a mimic of an ethylene/isobutylene polymer, made by the ADMET polymerization of a gem‐dimethyl substituted α,ω‐diene followed by hydrogenation of the polymer's repeat unit unsaturation. Chain termination reactants (CTR's) having one, three, and nine methylene “spacers,” respectively, between their olefin and alcohol precursor group were used to cap the polymer chain ends to yield 2.0 functional telechelics. Use of the medium length CTR in a polymerization–depolymerization scheme, resulted in amorphous (T_g = ?56 °C) telechelic diols with good molecular weight control.

     

Catalytic 1,3‐Cyclohexadiene Homopolymerization and Regioselective Copolymerization with Ethylene

Summary: 1,3‐Cyclohexadiene (CHD) was homo‐ and copolymerized by means of diimine nickel complexes and various substituted titanium based half‐sandwich complexes activated with methylaluminoxane (MAO). Soluble polycyclohexadienes were produced with the constrained geometry catalyst [Me₂Si(N^tBu)(Me₄Cp)]TiCl₂ (CBT) (Cp = cyclopentadienyl, Me = methyl). Only in the presence of CBT/MAO soluble high molecular weight CHD copolymers with ethylene were obtained. The CHD incorporation was varied between 0 and 12.3 mol‐%. According to NMR analysis the CHD/ethylene copolymerization is highly regioselective, accounting for exclusive formation of 1,4‐cyclohexene units randomly distributed in the polyethylene backbone.

¹³C NMR spectra of 1,4‐poly(1,3‐cyclohexadiene‐co‐ethylene) with 6.8 mol‐% CHD content in the copolymer.     

Water‐Soluble Building Blocks for Terpyridine‐Containing Supramolecular Polymers: Synthesis,Complexation, and pH Stability Studies of Poly(ethylene oxide) Moieties

Poly(ethylene oxide) of various molecular weights (M _n = 3 000, 5 200, 10 000, 16 500 g · mol^?1) has been modified with terpyridine end groups as building blocks for water‐soluble metallo‐supramolecular polymers. Metallo‐supramolecular A–A homopolymers have been prepared and characterized by complexing the terpyridine units of one selected poly(ethylene oxide) (M _n = 3 000 g · mol^?1) with the following transition metal ions in their 2+ oxidation state: Fe, Ru, Co, Ni, Cu, Zn, and Cd. In addition, the stability of the supramolecular connection with respect to pH variations has been investigated.

Schematic representation of the product of poly(ethylene oxide) modification with terpyridine end groups and the metal complexation.     

Synthesis and Properties of Hydrophilic Networks Based on Poly(ethylene glycol) and β‐Cyclodextrin

New hydrophilic networks combining poly(ethylene glycol) (PEG) and β‐cyclodextrin (β‐CD) have been prepared. Both components are linked by reacting PEG chains previously end‐capped with isocyanate groups and β‐CD, forming urethane links. Networks of molar compositions (β‐CD/PEG) ranging from 1/4 to 1/14, and with four different molar masses (400, 600, 900, and 1 350 g · mol^?1) of the end‐capped PEG precursor have been synthesized. The networks have good thermal stability and low glass transition temperatures. Crystallinity has only been detected for the two higher molar mass PEG precursors. The swelling properties of these hydrogels depend on the chain lengths of the PEG precursor and also on the temperatures.

     

Graft Polymerization of Methacrylamide onto Poly(ethylene terephthalate) Fibers with Benzoyl Peroxide as Initiator and their Characterization

Summary: The effects of polymerization temperature and time, initiator and monomer concentrations, ratio of water and solvent employed on the grafting of methacrylamide onto poly(ethylene terephthalate) fibers by the use of benzoyl peroxide initiator were studied. The graft yield was observed to increase with temperature and monomer concentration. The highest graft yield was obtained with an initiator concentration of 1 × 10^?2 mol/L. The rate of grafting was proportional to the power 0.48 and 1.6 of the methacrylamide and benzoyl peroxide concentrations, respectively. The overall activation energy for grafting calculated was 42.8 kcal/mol. The thermogravimetric data revealed that the thermal stability of poly(ethylene terephthalate) fibers decreased with grafting.

SEM micrographs of ungrafted PET fiber (a) and 44.9% MAAm‐grafted fiber (b).     

Two‐Dimensional ATR FT‐IR Spectroscopic Study on Glycol Diffusion in a Cured Epoxy Membrane

Summary: A novel experimental approach, that is, two‐dimensional (2D) correlation analysis based on time‐resolved attenuated total reflection (ATR) FT‐IR spectroscopy, has been used to study the diffusion behavior of ethylene glycol molecules into EP and EPB (novolac epoxy resins cured with novolac resin or novolac butyrate resin, respectively). The diffusion behavior of ethylene glycol into these systems is discussed and compared with that of water. Ethylene glycol absorbed in EP can be classified into two types (free and bound types), while in EPB a third type (referred to as “specific” type) is also observed, which differs from water sorption behavior. In particular, it is interesting to find that the hydrogen bonding of specific ethylene glycol involves two hydroxyl groups rather than one hydroxyl group and polar group in epoxy networks (carbonyl group), a similar example of which has not been previously observed. In addition, in both EP and EPB, bound ethylene glycol molecules diffuse faster than any other types.

Asynchronous 2D correlation spectra of ethylene glycol in the two resins studied here. Positive peaks are unshaded, whereas negative peaks are shaded.