Microwave-assisted polymerization process: A way to design new, high molecular weight poly(arylimidazole)s

In this paper, the microwave-assisted synthesis of high molecular weight poly(arylimidazole)s is described. These polymers were obtained by a one-pot polycondensation reaction involving a bis(α-diketone), an aromatic dialdehyde and ammonium acetate. Depending on the dialdehyde monomer, different poly(arylimidazole)s structures were synthesized. Structural characterization (¹H and ¹³C NMR), thermal properties (T_g, thermal stability) as well as a molecular weight determination of the polymers are reported.     

Synthesis of hyperbranched polymers via a facile self-condensing vinyl polymerization system - Glycidyl methacrylate/Cp2TiCl2/Zn

A facile self-condensing vinyl polymerization (SCVP) system, the combination of glycidyl methacrylate, Cp₂TiCl₂ and Zn, has been firstly used to prepare novel hyperbranched polymers, consisting of vinyl polymers as the backbone, and cyclic ester polymers (poly(?-caprolactone) or poly(l-lactide)) as the side chains. The polymerizations are initiated by the epoxide radical ring-opening catalyzed by Cp₂Ti(III)Cl which is generated in situ via the reaction of Cp₂TiCl₂ with Zn. The key to success is that the polymerizations can proceed concurrently via two dissimilar chemistries possessing the opposite active initiating species, including ring-opening polymerization (ROP) and controlled/living radical polymerization (CRP). We have demonstrated that this facile one-step polymerization technique can be applied successfully to prepare highly branched polymers with a multiplicity of end reactive functionalities including Ti alkoxide, hydroxyl and vinyl functional groups.     

熔融聚合法直接合成生物降解材料PGLA50/50

以等摩尔乙醇酸、L-乳酸为原料 ,通过熔融聚合法直接合成生物降解材料聚乙醇酸 -乳酸 (PGLA50 / 50 )。当在 1 65℃、70Pa下熔融聚合 1 0h ,以质量分数为 0 .5 %的氯化亚锡为催化剂时 ,产物特性黏数最高可达 0 .1 993dL/g。     

Simultaneous novel synthesis of conducting and non-conducting halogenated polymers by electroinitiation of (2,4,6-trichloro- or 2,6-dichlorophenolato)Ni(II) complexes

NiL₂(Ph)₂·xH₂O [L=3,5-dimethylpyrazole or N-methyl imidazole; Ph=DCP or TCP; x=0, 1 or 3] complexes were synthesised and characterised by analytical and spectroscopic methods using elemental analysis and FTIR. The electrochemical behavior of the complexes was studied by cyclic voltammetry in tetrabutylammoniumtetrafluoroborate-N,N-dimethylformamide electrolyte-solvent couple. Cyclic voltammogram of the complexes displayed two-step oxidation processes under the nitrogen gas atmosphere. The polymerization of the complexes was accomplished in the same solvent-electrolyte couple by the constant potential electrolysis of NiL₂(Ph)₂·xH₂O, synthesizing the poly(di- or monochlorophenylene oxide)s via free radical mechanism. The simultaneous polymerization of non-conducting polymer and conducting polymer (the conductivity of 0.7 S cm⁻²) were achieved by electroinitiated polymerization of Ni(DMPz)₂(TCP)₂. The structural analysis of the polymers were performed using FTIR, ¹H NMR and ¹³C NMR spectroscopic techniques and DSC for the thermal analysis. The kinetics of the polymerization was followed by in situ UV-vis spectrophotometer during the electrolysis. The low temperature ESR spectrum of the electrolysis solution also confirmed the formation of phenol radical (g=2.0028). One electron oxidation process of NiL₂(DCP)₂·xH₂O produces a new Ni(II) complex, Ni(L-L)(DCP)₂(S) by the rapid decomposition of Ni^IIIL₂(DCP)₂ into a ligand radical producing a singlet with the g value of 2.0015. Second electron oxidation process generates oligemers, which could not be isolated from the electrolyte solution.     

Ring-opening metathesis polymerisable charged platinum(II) complexes: Towards enhanced phosphorescent quantum yields by aggregation in polymers

Phosphorescent copolymers bearing a covalently linked charged platinum(II) dye were prepared using ring-opening metathesis polymerisation (ROMP). Absorption, emission as well as dynamic light scattering measurements of these polyelectrolytes indicate the formation of red luminescent aggregates in solution with quantum yields up to 17% and luminescence decay times in the range of 250-300 ns. Neither the quantum yield nor lifetime of the luminescence is affected by the presence of oxygen. The resulting polymers are solution processible and exhibit good film-forming properties. In contrast, the mononuclear platinum species are poorly soluble and non-luminescent at room temperature in deaerated solution.     

Synthesis and physicochemical characterization of a well-defined poly(butadiene 1,3)-block-poly(dimethylsiloxane) copolymer

For the first time, order-order and order-disorder transitions were detected and characterized in a model diblock copolymer of poly(butadiene-1,3) and poly(dimethylsiloxane) (PB-b-PDMS). This model PB-b-PDMS copolymer was synthesized by the sequential anionic polymerization (high vacuum techniques) of butadiene 1,3 (B) and hexamethylciclotrisiloxane (D₃), and subsequently characterized by nuclear magnetic resonance (¹H and ¹³C NMR), size exclusion chromatography (SEC), Fourier Transform infrared spectroscopy (FTIR), Small-Angle X-ray scattering (SAXS) and rheology. SAXS combined with rheological experiments shows that the order-order and order-disorder transitions are thermoreversible. This fact indicates that the copolymer has sufficient mobility at the timescale and at the temperatures of interest to reach their equilibrium morphologies.     

含稠杂环结构聚醚酮酮的合成与性能研究(I)

以吩噻（ＯＳＰ）、对苯二甲酰氯（ＴＰＣ）和二苯醚（ＤＰＥ）为单体,在无水ＡｌＣｌ３／ＣＨ２ＣｌＣＨ２Ｃｌ／ＤＭＦ催化剂／溶剂体系中,由亲电缩聚反应合成了含稠杂环结构的聚醚酮酮共聚物,并对其基本性能进行了测定。结果表明,含ＯＳＰ结构单元ＰＥＫＫ的Ｔｇ比全对苯基位ＰＥＫＫ高４２℃以上。且随ＯＳＰ结构单元含量的增加,共聚物Ｔｇ逐渐提高,而Ｔｍ、结晶度却逐渐下降,仍具有很好的耐热性和耐溶剂性。     

One-pot synthesis and characterization of aliphatic poly(oxytetramethylene) ionene

One-pot synthesis of poly(oxytetramethylene) ionene (POI) composed of one dimethylammonium group in each repeating unit is described. POI was prepared by using the cationic polymerization of tetrahydrofuran, followed by the chain extension reaction of living poly(oxytetramethylene) (POTM) chain with N,N-dimethylaminotrimethylsilane. The weight average molecular weight of the ionene with bromide counter-anion (POI-Br) was 48,000 g/mol and the molecular weight of POTM between the ionic sites was ca. 2100. POI-Br showed polyelectrolyte behavior in polar solvent. The elastomeric film of POI-Br was prepared: its tensile strength at break and elongation at break were ca. 11 MPa and ca. 1900% at 19 °C, respectively. Small-angle X-ray scattering, differential scanning calorimetry and dynamic mechanical analysis suggested the formation of microphase-separated structure for POI-Br film.     

Spontaneous zwitterionic copolymerisation: An undervalued and efficacious technique for the synthesis of functional degradable oligomers and polymers

The spontaneous zwitterionic copolymerisation (SZWIP) of compatible nucleophilic and electrophilic monomers is a relatively unknown and unexplored method for the synthesis of (predominantly alternating) degradable co- and terpolymers. A wide range of monomers allows for the synthesis of different polymer classes with various functionalities, including poly(aminoester)s, poly(ester amide)s and poly(phosphoester)s. In this review, we discuss this undervalued copolymerisation method and its potential for the facile preparation of functional polymeric systems. In this context, the polymers synthesised to date by SZWIP as well as recent insights into this polymerisation technique are highlighted. Post-polymerisation modifications and applications of polymers obtained by SZWIP are also discussed.     

Temperature responsive bio-compatible polymers based on poly(ethylene oxide) and poly(2-oxazoline)s

This review covers the LCST behavior of two important polymer classes in aqueous solution, namely poly(2-oxazoline)s and systems whose thermo-responsiveness is based on their structural similarity to poly(ethylene oxide) (PEO). In order to elucidate the progress that has been made in the design of new thermo-responsive copolymers, experimental data that were obtained by different research groups are compared in detail. Copolymerization with hydrophilic or hydrophobic comonomers represents a suitable method to tune the coil to globule transition temperature of several homopolymers, and incorporation of other monomers provided further interesting features, such as pH responsiveness or sensing properties. In addition, living and controlled polymerization techniques enabled access to defined end groups and more advanced polymer architectures, such as graft copolymers or double responsive block copolymers. The effect of such structural variations on the temperature responsive behavior of the (co)polymers is discussed in detail.     

Synthesis of novel nanoreinforcements for polymer matrices by ATRP: Triblock poly(rotaxan)s based in polyethyleneglycol end-caped with poly(methyl methacrylate)

Poly(rotaxan)s of poly(ethylene glycol) and α-cyclodextrines (CD) block copolymers end-capped with poly(methyl methacrylate) chains were synthesized by atom transfer radical polymerization. The synthesized copolymers were characterized by ¹H NMR, 2D NOESY NMR, X-ray and Thermogravimetric analysis. Assuming a maximum relation of 2 CDs per ethyleneglycol unit, a coverage degree of 18% and 15% was achieved. X-ray analysis showed a characteristic signal around 20θ for all copolymers with an amorphous halo mainly due to inter-crystal poly(ethylene glycol) and poly(methyl methacrylate) chains. Full Molecular Dynamics of 20 ns was used to simulate the crystal structure of these copolymers. A pair correlation function was used to determine the coupling between hydrogen atoms of PEG, PMMA and cyclodextrine obtained by 2D NOESY NMR.     

The role of ion and solvent transport during the redox process of conducting polymers

The understanding of the redox behavior of conducting polymers is essential for a successful application of these so-called synthetic metals as functional coatings. The redox process involves the exchange of ions and solvent molecules. This so called doping/dedoping process involves changes of the mechanical and the electronic structure of the polymer. This paper discusses investigations at poly(3,4-ethylenedioxythiophene (PEDOT) and poly(pyrrole) (Ppy) by the electrochemical quartz crystal microbalance (EQCM) technique and electrochemical impedance spectroscopy (EIS). In the case of PEDOT a determination of the anion and the solvent fluxes was possible, and it was found that most anions replace solvent molecules upon their incorporation. The doping/dedoping mechanism of Ppy is more complicated. Here, the first redox cycles are characterized by a complex interplay of cation, anion and solvent fluxes with irreversible changes of the polymer structure. However, in combination with EIS new insights of the ion and solvent exchange and its influence on the electronic properties can be achieved.     

Synthesis and characterization of conducting and non-conducting polymers of sodium 2,4,6-trichlorophenolate by microwave initiation

A novel synthesis of poly(dichlorophenylene oxide) and a conducting polymer were achieved simultaneously from 2,4,6-trichlorophenol in a very short time, using microwave energy. The characterizations of poly(dichlorophenylene oxide) and the conducting polymer were performed by DSC, TGA, elemental analysis, FTIR, ¹H and ¹³C NMR, SEM, MS and X-ray diffraction spectrometer analyses. The combined molecular weight of the polymer, 1.8×10⁴, was determined by using viscometry measurement. Poly(dichlorophenylene oxide) displaces selectivity in the favor of mainly 1,2-addition structure. The optimum conditions for the polymer and the conducting polymer synthesis were 70 W for 5 min and 100 W for 1 min, respectively. The direct synthesis of highly conducting polymer, with the conductivity of 0.3 S cm⁻² were achieved in the absence of applied doping process in a very short time sequence. Conductivity-temperature relation was examined for the conducting polymer.     

Synthesis of poly(vinyl alcohol) combs via MADIX/RAFT polymerization

Poly(vinyl acetate) combs have been prepared via macromolecular design via interchange of xanthate (MADIX)/reversible addition-fragmentation chain-transfer (RAFT) polymerization using xanthate functionalized polymer cores. The comb backbones were prepared using well-defined poly(vinyl alcohol) PVA polymers with a degree of polymerization of 20, 100 and 170, respectively. Functionalization with xanthates via R-group or a Z-group approach resulted in the formation of macromolecular MADIX agents. While Z group designed macromolecular xanthate agents appeared to inhibit the polymerization of vinyl acetate (VAc), R group designed macromolecular xanthate agents achieved to mediate efficiently the bulk polymerization of VAc affording PVAc combs. However, the growth of the combs was accompanied at low conversions by the formation of linear polymer chains as a result of the constant initiation (AIBN) and shoulders, which can be attributed to intermolecular coupling reactions. The proportions of single chains and termination products were observed to increase with the degree of polymerization of the macromolecular MADIX agents broadening the molecular weight distribution. As a result of a stable ester link between the branches and the PVA backbone, the branched PVAc architectures were finally hydrolyzed to afford poly(vinyl alcohol) combs.     

Synthesis, characterizations and properties of new copoly(aryl ether)s with alternate hole- and electron-transporting fluorophores

Three novel copoly(aryl ether)s, consisting of alternate isolated hole-transporting (2,5-dihexyloxy-1,4-distyrylbenzene) and electron-transporting (p-quaterphenyl or aromatic 1,3,4-oxadiazole) segments, were synthesized from corresponding bis(phenol) and bis(fluoride) monomers by nucleophilic displacement reaction. These copolymers are soluble in common organic solvents and exhibit good thermal stability with 5% weight loss temperature above 400 °C in nitrogen atmosphere. The photoluminescent (PL) spectra and quantum yields of these copolymers are dependent on the composition of the isolated fluorophores. The HOMO and LUMO energy levels of these copolymers have been estimated from their cyclic voltammograms. All the observations directly proved that the oxidation in copolymers starts at the hole transporting segments. Moreover, the electron and hole affinities can be enhanced simultaneously by introducing isolated hole-transporting and electron-transporting segments, in which p-quaterphenyl is more electron-affinitive than aromatic 1,3,4-oxadiazole chromophores.     

The ROMP toolbox upgraded

This article features the current state of research in olefin metathesis polymerization techniques towards the synthesis of functional polymeric materials. Emphasis is laid on work making use of ring opening metathesis polymerization (ROMP) initiated by ruthenium complexes published in the last five years. Other techniques such as alternating diene metathesis polymerization (ALTMET) are only covered when appropriate. A survey on polymer architectures accessible via olefin metathesis is presented and illustrated with manifold examples from research fields like life science, optics and electronics, sensorics or energy storage. Important new developments such as end-group functionalization or stereoselective polymerization are addressed. A chapter on using alternative and green solvents in ROMP is disclosed as well as an overview on the use of olefin metathesis polymerization using sustainable substrates. Applications in material science such as porous, liquid crystal or self-healing materials close the work.     

The infulence of aromatic diols on thermotropic Poly(ester-amide)s synthesized by direct polycondensation

Thermotropic Poly(ester-amide)s containing triethyleneglycol bis(4-carboxyphenyl) ether (PEG₃), o-Tolidine (OT) and various aromatic diols such as hydroquinone (HQ) and 4,4-biphenol (BP) were synthesized by direct polycondensation with DPCP (diphenyl chlorophosphate) as direct condensation agent in the presence of pyridine and LiCl. The polymer structures were characterized by infrared spectroscopy and elemental analysis. The influence of structure, substituents and contents of various aromatic diols on the phase transitions were studied by Differential Scanning Calorimetry (DSC) and Polarized Optical Microscopy. These revealed that the structure and substituents of diols affected the mesophase while most of the synthesized polymers exhibit nematic mesophase. Addition of HQ decreased the melting temperature of the polymers, but, in contrast to others diols, did not affect thermal resistance.     

Influence of reaction parameters on the synthesis of hyperbranched polymers via reversible addition fragmentation chain transfer (RAFT) polymerization

The synthesis of hyperbranched poly(methyl methacrylate) (PMMA) via reversible addition fragmentation chain transfer (RAFT) polymerization was investigated by varying the ratio chain transfer agent (CTA): monomer (methyl methacrylate, MMA): brancher (ethylene glycol dimethyl methacrylate, EGDMA): free radical initiator (AIBN) at various temperatures (50, 55, 60, 65, 70 °C). The rate of polymerization was observed to increase with temperature and concentration in brancher, whilst it was lowered by an increase in chain transfer agent concentration. The molecular weight of the samples increased with the ratios brancher: CTA and monomer: CTA. The polydispersity of the samples increase with conversion, as the level of branching increases. At fixed concentration in brancher, an increase of CTA concentration led to polymers with lower PDI. The variation of enthalpy and entropy relative to the monomer reaction were calculated, and it was observed that an increase in the brancher concentration induced an increase in both and , whilst lower CTA concentrations led to an increase in . The variation in Gibbs energy for the monomer reaction was calculated at 60 °C, and results confirmed the presence of a retardation effect when increasing CTA concentration generally observed in RAFT polymerization.     

Polyisobutylene-based miktoarm star polymers via a combination of carbocationic and atom transfer radical polymerizations

Poly(isobutylene-b-styrene) (PIB-PS) copolymers and polyisobutylene (PIB) homopolymers were synthesized via quasiliving carbocationic polymerization from the initiator 3,3,5-trimethyl-5-chlorohexyl acetate, which contains a protected hydroxyl group. The PIB block was created at −70 °C in a methylcyclohexane/methyl chloride (60:40) cosolvent system, using TiCl₄ as co-initiator, followed optionally by sequential addition of styrene. Using a strong base, the acetate head group of the resulting block copolymer was cleaved to yield a hydroxyl group, which was subsequently esterified with the branching agent 2,2-bis((2-bromo-2-methyl)propionatomethyl)propionyl chloride (BPPC) to create dual initiating sites for atom transfer radical polymerization (ATRP). ATRP of tert-butyl acrylate was carried out using a Cu(I)Br/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) catalyst system. In some cases, the ester side chains of the poly(tert-butyl acrylate) (PtBA) blocks were cleaved to create poly(acrylic acid) (PAA) blocks. The final miktoarm star polymers had compositions that were very close to theoretical.