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.     

Synthesis of Defined Poly(silsesquioxane)s: Fast Polycondensation of Trialkoxysilanes in a Continuous‐Flow Microreactor

The polycondensation of trialkoxysilanes to PSSQs in a microreactor setup is demonstrated. While continuous‐flow processes involving microreactors found various applications in chain growth polymerization, their influence on step‐growth polymerization is less explored, and the polycondensation of multifunctional monomers has not been studied in detail. We found significantly increased yields and a decreased polydispersity of the obtained polymers in comparison to the batch process. By variation of the residence time molecular weights could be adjusted reproducibly ranging from = 1 900 to 11 000 g · mol^?1. Thus, the microreactor setup offers for the first time the possibility to synthesize PSSQ with adjustable properties.

     

Poly(carbazole)‐Based Copolymers Containing Deep‐Blue Chromophore for Polymer Light‐Emitting Diode Applications

A new series of two poly(carbazole)‐based copolymers (poly(9‐hexyl‐carbazole‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PCVz) and poly(9,9‐dioctylfluorene‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PFCVz)) containing carbazoylphenylquinoline pendant groups were synthesized via the Suzuki coupling reaction for polymer light‐emitting diode applications. The electro‐optical properties of ITO/PEDOT/Polymer/PBD/LiF/Al devices based on these copolymers were investigated using UV‐visible, photoluminescence, and electroluminescence spectroscopy. The turn‐on voltages of the copolymer devices were found to be 6.0–8.0 V. The maximum brightness and luminescence efficiency of the copolymers device were found to be 230 cd · m^?2 and 0.28 cd · A^?1 at 11 V, respectively.

     

FTIR‐Spectroscopy on Segmental Reorientation of a Nematic Elastomer under External Mechanical Fields

Summary: Fourier transform infrared (FTIR) spectroscopy with polarized light is employed to study the segmental orientation and the order of a nematic liquid crystalline elastomers (NLCEs) with a monodomain structure in response to an external mechanical field. The reorientation and the order parameter of the different molecular moieties are analyzed in detail, revealing information about angular excursion in the rearrangement of the mesogens, the spacer molecules, and the main‐chain. In case of an elongation of the NLCE films perpendicular to the initial mesogen orientation, no reorientation or change of order is observed for an elongation ratio less than 1.3. At higher strain, a molecular reorientation process is induced on all molecular segments and the order of alignment is decreased. When the NLCE‐films are stretched parallel to the mesogens, no molecular reorientation takes place and the order parameters show no significant change.

Angular reorientation of different molecular moieties at mechanical strain perpendicular to the initial mesogen orientation.     

Functional Thin Polymer Films at High Pressure

Summary: A new thin‐film characterization setup was created based on the combination of a surface plasmon spectrometer with an electrochemical cell operated under high pressure of up to 200 MPa and at temperatures up to 120 °C. The examples given to document its performance include photoisomerization studies with poly(methyl methacrylate) (PMMA) films partly derivatized with disperse red (DR1), as well as, a preliminary account of the electropolymerization of EDOT under pressure and the assessment of the redox properties of the resulting thin PEDOT films.

Sketch of the high‐pressure electrochemistry surface plasmon cell.     

Quantitative Analysis of Dielectric Constants from EFM Images of Multicomponent Polymer Blends

Summary: A simple quantitative model for the analysis of EFM images of three‐ or more‐component polymer blends is applied to determine the dielectric constants of the blend constituents. The value of the dielectric constant of PIPA calculated from the EFM images of POMA‐PIPA‐APP blend is determined in good agreement with the literature value.

     

Synthesis,Electrochemical and Photovoltaic Properties of Multi‐Armed Polythiophenes with Triphenylamine Trivinylene as Conjugated Linker

Three polythiophenes with 5%, 10% and 15% triphenylamine trivinylene (TPAV) as bridge linker, PT‐TPAV5, PT‐TPAV10 and PT‐TPAV15, were synthesized. The Wittig‐Horner‐Emmons reaction and the Stille method were employed to synthesize these polymers. The polythiophenes were subsequently used in bulk‐heterojunction polymer solar cells (PSCs) as donor materials. The polymers exhibited a striking and reversible color change after the oxidation of the polymer films. The power conversion efficiencies of the PSCs based on PT‐TPAV5, PT‐TPAV10 and PT‐TPAV15 as donors and PCBM as acceptor were 0.17%, 0.50%, and 0.35%, respectively, under the illumination of AM 1.5, 100 mW · cm^?2.

     

Metathetic Selective Degradation of Polyisoprene: Low‐Molecular‐Weight Telechelic Oligomer Obtained from Both Synthetic and Natural Rubber

Summary: Degradation studies of cis‐1,4‐polyisoprene were carried out using first and second generation Grubbs catalysts to achieve end‐functionalized acetoxy oligomers in both an organic solvent and a latex phase at room temperature. Well‐defined acetoxy telechelic polyisoprene structures were obtained in a selective manner with a range of from 10 000 to 30 000, with a polydispersity index of around 2.5.

Structure produced by the metathetic depolymerization of hydroxy telechelic cis‐1,4‐polyisoprene.     

Protonation of Sulfonated Poly(4,4′‐diphenylether‐1,3,4‐oxadiazole) Membranes

This work describes the effect of sulfuric acid protonation on the properties of SPOD‐DPE membranes using FT‐IR and impedance spectroscopic analyses. The IR spectra showed the protonation of nitrogen atoms from oxadiazole rings, with a broad band complex in the region 3 000–2 100 cm^?1 with two centered peaks at 2 590 and 2 440 cm^?1. The S?O characteristic absorption bands in SPOD‐DPE and sulfuric acid were specially studied in the region of 1 800–900 cm^?1. The band shifts are associated to the interaction between acid groups and oxadiazole ring nitrogen atoms. The IR spectra evidenced the presence of three absorption species (HSO, SO and free H₂SO₄) depending on the sulfuric acid concentration. For the protonated SPOD‐DPE membranes, a proton conductivity around 10 mS · cm^?1 was reached at 50 °C.

     

Control of the radical polymerization by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl and its sodium salt

The control of the radical polymerization of styrene by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl is reported here in bulk at 90 °C, 120 °C and in miniemulsion. Similarly, the control by its sodium complex is reported in bulk at 90 °C.

M _n vs. conversion for 3 , 3Na , and TEMPO.     

Chain Growth Polycondensation as a Polymer Generating Reaction in the Synthesis of Oligo(p‐phenyleneethynylene)s with Low Polydispersity

Summary: The polycondensation of 1‐ethynyl‐2,5‐dihexyl‐4‐iodobenzene in the presence of 1‐ethynyl‐2,5‐dihexyl‐4‐(2‐phenylethynyl)benzene proceeds according to the mechanism of initiated chain growth polycondensation. It has allowed the synthesis of oligomers with a desired molecular weight and a narrow molecular weight distribution. The reasons for the side reaction leading to the formation of diyne compounds are revealed and the presumed mechanism is given. This opens prospects for the preparation of defectless poly(p‐phenyleneethynylene)s with required molecular weights and narrow molecular weight distributions.

     

Electrochemical Polymerization of Thianaphthene in Mixed Electrolytes of Boron Trifluoride Diethyl Etherate and Trifluoroacetic Acid

Substrate‐supported polythianaphthene (PTN) films have been electrochemically synthesized by direct oxidation of thianaphthene on platinum or stainless steel electrode in mixed electrolytes of boron trifluoride diethyl etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potentials of the monomer in these media are considerably lower than those in neutral solvents. Increasing the content of TFA in the mixed electrolytes can effectively decrease the oxidation potential and increase the coupling rate of the monomer. On the other hand, a high TFA concentration can result in a negative effect on the properties of the as‐formed polymer. The mixed electrolyte of BFEE + 16.7% TFA was found to be the most suitable medium for the electrosyntheses of PTN. PTN in dedoped state is soluble in usual strong polar organic solvent such as dimethyl sulfoxide (DMSO). Fluorescent spectral studies indicate that the polymer is a blue light emitter.

     

Poly(neopentylene carbonate) Hyperstars

Summary: Branched aliphatic polycarbonates were synthesized by ring opening polymerization of 5,5‐dimethyl‐1,3‐dioxane‐2‐one (NPC) initiated from polyfunctional alcohols and a commercial hyperbranched polyester (BOLTORN®). Polymerizations in the presence of fumaric acid under bulk conditions allowed high conversion (80%) without gelation. The synthesis of polymers with long chain branches was confirmed by size exclusion chromatography and universal calibration. The Mark–Houwink exponent decreased, indicating an increased density, while increasing the number of arms. The star polymers with up to four arms showed thermal properties T_g (20–30 °C) and T_m (100–110 °C) similar to linear PNPC.

Boltorn? hyperbranched polymer with radial polycarbonate grafts.     

Synthesis and Dielectric Study of New Liquid‐crystalline Polysiloxanes Presenting a Thioether Spacer

Three new cyanobiphenyl polysiloxanes presenting long thioether spacers have been carried out. This type of spacer leads to very stable liquid‐crystalline polymers at room temperature and remove the crystallinity phenomenon. Dielectric analysis results show that the thioether spacer brings much more molecular flexibility to the system.

Example of an “interdigitated” structure observed by X‐ray analysis.     

Morphology and Phase Characteristics of High‐Density Polyethylene Probed by NMR Spin Diffusion and Second Moment Analysis

Summary: A dipolar filter pulse sequence combined with cross‐polarization‐MAS is applied to characterize the phase distribution, morphology, and spin diffusion within a high‐density polyethylene sample. A new method to obtain quantitative ¹³C NMR by combining cross‐polarization‐MAS and spin diffusion NMR is presented. The derived crystallinity is consistent with the corresponding crystallinity obtained by ¹H NMR.

Illustration of the pulse sequence(s) applied in the present work.     

Synthesis and Electroluminescent Properties of Disubstituted Polyacetylene Derivatives Containing Multi‐Fluorophenyl and Cyclohexylphenyl Side Groups

A new series of disubstituted polyacetylene derivatives that contain multi‐fluorine atoms on the pendent phenyl ring have been synthesized and characterized. The results reveal a greater red‐shift in UV‐vis absorption and PL emission upon incorporating more fluorine atoms on the pendent phenyl ring. Among them, disubstituted polyacetylene with a difluorophenyl group ( PDPA‐2F ) showed the highest luminescent efficiency. The device performance can be promoted by blending a hole‐transporting material TM‐TPD into PDPA‐2F as the active layer or by using a light‐emitting copolymer in which PDPA‐2F was copolymerized with a carbazole group ( PDPA‐2Fcab ). A light‐emitting diode of ITO/PEDOT/ PDPA‐2Fcab /Ca/Al revealed a maximum luminescence of 4230 cd · m^?2 at 14 V and a maximum current efficiency of 3.37 cd · A^?1 at 7 V.

     

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.

     

Cocrystallization of Blends of Ethylene/1‐Olefin Copolymers: An Investigation with Crystallization Analysis Fractionation (Crystaf)

Summary: Crystallization analysis fractionation (Crystaf) is a technique for estimating the chemical composition distribution (CCD) of semi‐crystalline copolymers. Cocrystallization may happen during Crystaf analysis, affecting Crystaf profiles and leading to misinterpretation of the CCD. This study investigates this phenomenon and determines the main factors leading to cocrystallization by analyzing a series of ethylene/1‐olefin copolymers. We considered three factors affecting cocrystallization: comonomer type, cooling rate and chain crystallizability. The results showed that cooling rate and similarity in chain crystallizability are the key factors regulating cocrystallization during Crystaf analysis.

Crystaf analysis of blends of copolymers.     

Evidence of Intramolecular Cyclization in Copolymerization of Ethylene with 1,3‐Butadiene: Thermal Properties of the Resulting Copolymers

Summary: Ethylene and butadiene were copolymerized with a silylene‐bridged bis(fluorenyl) complex {[Me₂Si(C₁₃H₈)₂]NdCl} ( 1 ) in combination with various alkylating agents (BuLi/AlH(iBu)₂, (Bu)MgCl, Mg(Bu)(Oct)). Copolymers have a unique microstructure since they contain 1,2‐cyclohexane rings and unsaturations along the polymer chain. An intramolecular mechanism was proposed for the formation of six‐membered rings. The influence of these cyclic structures on thermal properties of the copolymers has been investigated.

Proposed mechanism for formation of 1,2‐cyclohexane rings.     

A Study of Copolymerization of 1‐Hexene with 2,5‐Norbornadiene Using Metallocene Catalysts

Summary: Copolymerization of 1‐hexene with a symmetrical diene, namely 2,5‐norbornadiene was studied using four different metallocene catalysts. Copolymerization was found to occur exclusively through one of the two equally reactive endocyclic double bonds with all the four catalysts. Copolymerization results in low molecular weight oligomers with the number average molecular weight ( ) varying from 1 000–3 000. End group analysis of the co‐oligomers revealed that the β‐hydrogen transfer after 2,1 insertion also occurs in the presence of highly regiospecific catalysts. The regio errors were also found to depend on various reaction parameters such as polymerization time, Al/Zr mol ratio, metallocene concentration and polymerization temperature.

Plots of variation in end groups and NBD incorporation with time.