Cyclic Ladder Polymers by Polycondensation of Silylated Tetrahydroxy‐tetramethylspirobisindane with 1,4‐Dicyanotetrafluorobenzene

Summary: 5,5′,6,6′‐Tetra(trimethylsiloxy)‐4,4,4,4′‐tetramethyl‐1,1‐spirobisindane was polycondensed with 1,4‐dicyanotetrafluorobenzene under variation of solvent temperature, time, and feed ratio. Under optimized reaction conditions, all products detectable by MALDI‐TOF mass spectrometry (up to masses around 8 000 Da) proved to be cyclic ladder oligomers and polymers. In N‐methylpyrrolidone and dimethylsulfoxide odd‐numbered cycles were formed in addition to the prevailing even‐numbered ones. However, in sulfolane exclusively even‐numbered cycles were obtained (detectable up to masses around 10 000 Da), together with even‐numbered linear chains. Temperatures above 100 °C enhanced the molecular weights by side reactions. With the less reactive cyano‐2,3,5,6‐tetrafluorobenzene (CTB) again cycles were formed, but their content and the conversions were lower. Polycondensation of CTB up to 160 °C and all polycondensations of cyanopentafluorobenzene gave crosslinked products.

Synthesis of cyclic ladder polymers.     

Dual Tuning of Emission Color and Electron Injection Properties Through in‐situ Chemical Reaction in a Conjugated Polymer Containing 9,10‐Phenanthrenequinone

Three new polymers were obtained through an in situ chemical reaction of the matrix conjugated polymer ( PPQF ) with ortho‐amine compounds. By controlling the conjugation degree of diamine compounds, the emission of PPQF was tuned from weak blue to bright blue, green, and orange for PFBQ , PFBP and PFNP , respectively. The photoluminescence efficiencies were also improved in the same tendency, and the LUMO levels were gradually decreased from ?2.76 and ?3.12 to ?3.40 eV, which was beneficial for electron injection and transport in electronic devices. Thus, a dual tuning for the emission color and electron injection properties were realized through an in situ chemical reaction, which is a novel strategy to design and construct new valuable polymers from one reactive matrix polymer.

     

Thermosetting Resins Based on a Self‐Crosslinkable Monomer/Polymer Possessing Meldrum's Acid Groups

Thermosetting resins based on Meldrum's acid (MA) derivatives as monomers show high thermal stability and inherent low‐dielectric constants. In this work, a multifunctional MA derivative (MA‐bisF) possessing two MA and two furan groups is newly prepared. Characterization of MA‐bisF has been carried out with Fourier transform infrared, ¹H NMR, mass spectroscopy, and elemental analysis. Self‐crosslinking MA‐bisF results in the corresponding thermosetting resin mediating the addition reaction between ketene/ketene and ketene/furan groups. MA‐bisF is also utilized as a modifier for bismaleimide (BMI) resins through polymerizing MA‐bisF and BMI through Diels–Alder reaction. The corresponding crosslinked MA‐bisF/BMI resin possesses a high content of fused‐ring structure and a high crosslinking density, so as to exhibit high thermal stability (392 °C), high glass transition temperature (262 °C), high char yield (48 wt%), and a low‐dielectric constant of 2.78 at 1 MHz. A new type of reactive polymers and the corresponding high‐performance crosslinked resins has been demonstrated.

     

Preparation of Inclusion Complexes between Amylose and Ester‐Containing Polymers by Means of Vine‐Twining Polymerization

This paper reports the preparation of inclusion complexes of amylose with synthetic polymers by means of enzymatic polymerization of α‐D ‐glucose 1‐phosphate monomer (Glc‐1‐P). The synthetic polymers, employed as the guests, are poly(ε‐caprolactone), poly(δ‐valerolactone), and poly(ester‐ether), containing ester groups in the main chains. The formation of the inclusion complexes was carried out by the enzymatic polymerization of Glc‐1‐P catalyzed by phosphorylase in the presence of the guest polymers.

     

Formation of Macrozwitterions in the polymerization of β-propiolactone initiated by betaine. 4th Communication on Macrozwitterions

The anionic polymerization of β-propiolactone at 25°C in ethanol initiated by the betain \documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_3 )_3 \mathop {\rm N}\limits^ \oplus - {\rm CH}_{\rm 2} {\rm COO}^ \ominus $\end{document} was investigated. Macrozwitterions of the structure were produced, n being intentionally as low as ca. 11. The structure of the product was proven by the nitrogen content of the reprecipiated polymer, by IR and NMR spectroscopy and by titration of the carboxylate endgroups. Some carboxylic acid endgroups were formed by chain transfer with the solvent ethanol. The positive charge at the polymer chain was proven by electrophoresis of polymer after esterification of the carboxylate chain end. Furthermore the dielectric constant of dilute solutions of the polymer in CHCl₃ was determined and is discussed. The kinetics of the polymerization process were investigated by IR-spectroscopy. The initiation reaction between monomer and betain is about 5 times slower than the consecutive propagation by addition of monomer to the anionic chain end.     

Novel Fluorinated Hybrid Polymer by Radical Polyaddition of Bis(α‐trifluoromethyl‐β,β‐difluorovinyl) Terephthalate onto Dialkoxydialkylsilanes

To develop the radical polyaddition of bisperfluoroisopropenyl esters, the reactions of bis(α‐trifluoromethyl‐β,β‐difluorovinyl) terephthalate [CF₂?C(CF₃)OCOC₆H₄COOC(CF₃)?CF₂] (BFP) with dialkoxydialkylsilane were examined to prepare fluorinated hybrid polymers bearing dialkylsilyl groups in the main chain. Prior to polyaddition, the radical addition reaction of 2‐benzoyloxypentafluoropropene [CF₂?C(CF₃)OCOC₆H₅] (BPFP) has been investigated to afford the results that diethoxydimethylsilane (DEOMS) or dimethoxydimethylsilane with BPFP initiated by oxo radical are the best combination for the preparation of polymers. The mechanism of the addition reaction was proposed. Radical polyaddition of BFP with DEOMS initiated by benzoyl peroxide or di‐tert‐butyl peroxide has yielded polymers of up to molecular weight 1 × 10⁶ with rather broad molecular weight distribution. A mechanism for the polyaddition reaction is proposed based on the radical addition reaction between BPFP and DEOMS. The step‐growth polymerization is initiated by hydrogen abstraction of DEOMS to add a perfluoroisopropenyl group, followed by a 1,7‐shift of the radical in the intermediate. The relationship between addition reaction mechanism and polyaddition mechanism was also discussed.

     

Über die polymerisation des 2-chlor-2-oxo-1.3.2-dioxaphospholans

Polymerization by ringopening of 2-chloro-2-oxo-1.3.2-dioxaphospholane ( I ) may lead to polymers of two different structures: (i) a polymeric acid chloride possessing a polyester structure of the main chain ( II ) and ( ii ) a β-chloroethyl ester of polyphosphoric acid, i.e. a polymer with a pure inorganic main chain ( III ). I is transformed into a polymer with a t least 90% of structure I11 and with at most 10% of structure I1 by heating or more rapid by and under more gentle conditions with various catalysts (e.g. NaF, AlCl₃, N(CH₃)₄Cl, tetraphenylphosphonium salts, triphenyl-phosphine, triphenylphosphine oxide). The product is branched and crosslinked. Kinetic measurements show that the spontaneous polymerization follows another mechanism than the catalytic reaction. The results are compatible with the assumption that the pure thermal reaction proceeds by successive independent steps, whereas the catalytic process advances via an ionic chain reaction. The effect of the various catalytic active substances consists in the direct or indirect production of chloride ions, which are on their part the real catalytic species.     

Synthesis of Helical Poly(Phenyleneethynylene‐Pyromellitic Diimide)s and the Responsiveness of the Helicity to Solvents,Heat, and pH

N,N′‐bis‐(L ‐4′‐iodophenylalanine octyl ester)pyromellitic diimide ( 1 ) was synthesized, and the Sonogashira–Hagihara coupling polymerization of 1 with para‐/meta‐diethynylbenzenes ( 2p / 2m ) was carried out to obtain optically active phenyleneethynylene‐based polyimides carrying ester groups [poly( 1 ‐ 2p ) and poly( 1 ‐ 2m )] with number average molecular weights in the range from 4 900 to 19 700 in 68–80% yields. The polymers were satisfactorily converted into the corresponding polymers carrying free carboxy groups [poly( 1 ‐ 2p )′ and poly( 1 ‐ 2m )′] by alkaline hydrolysis. All the polymers exhibited intense CD signals, indicating that they formed helices with predominantly one‐handed screw sense. The helical conformations of the polymers were stable against heat. Poly( 1 ‐ 2p )′ and poly( 1 ‐ 2m )′ lost the one‐handed helicity by the addition of NaOH, and the resultant polymer recovered the original conformation upon HCl addition.

     

Phenyleneethynylene Macrocycle‐Fused Phenylacetylene Monomers: Synthesis and Polymerization

Phenyleneethynylene macrocycle‐substituted acetylenes were synthesized by repetition of the Sonogashira coupling reaction, and the elimination reaction of the terminal acetylene protecting group. The monomers were polymerized with a rhodium catalyst, [Rh(nbd)Cl]₂, at the terminal acetylene unit, and the polymerization mixtures were purified by precipitating into methanol to yield the corresponding poly(phenylacetylene) derivatives as yellow‐red powders, which had a high degree of polymerization ( ≈ 500) in spite of their steric bulkiness. The trimethylsilyl and pentamethyldisiloxanyl groups of polymers improved their solubility, and the polymers were soluble in common organic solvents, such as toluene, chloroform and tetrahydrofuran.

     

Products from the reaction of diphenyl ether with formaldehyde. Resins from formaldehyde. 86

From the reaction products of diphenyl ether with formaldehyde in the presence of acidic catalysts, six compounds were purely isolated: p-methylol and p,p′-dimethylol diphenyl ether, and four compounds of the following structures: Their structures were identified by the IR-absorptions and by the synthesis of their derivatives.     

Synthesis and Characterization of Surface Functional Polymer Nanoparticles by a Bottom‐Up Approach from Tailor‐Made Amphiphilic Block Copolymers

Core‐crosslinked nanoparticles presenting secondary amine functional groups in the hydrophilic shell are synthesized by a bottom‐up approach. The route utilizes polymerization of 2‐oxazolines to prepare tailor‐made block copolymers with a primary or secondary amine end group in the hydrophilic block and alkynyl moieties in the hydrophobic part of the polymer. Upon solubilization in the aqueous media, these block copolymers form micelles that are photocrosslinked by a radical polymerization process to afford two types of core‐crosslinked nanoparticles, either with secondary amines, NP1, or primary amines, NP2, on the surface. The dimensions and stability of the core‐crosslinked nanoparticles are characterized by dynamic light scattering and fluorescence spectroscopy. The availability and reactivity of the amine groups in the hydrophilic shell are demonstrated by reaction with different aromatic model compounds resulting in a degree of surface functionalization of 4–47% for NP1 nanoparticles with secondary amino groups and a 20–95% degree of surface functionalization for NP2 with primary amine groups, as determined by UV–vis spectroscopy.

     

Mixed Alkyl‐ and Alkoxy‐Substituted Poly[(phenylene ethynylene)‐alt‐(phenylene vinylene)] Hybrid Polymers: Synthesis and Photophysical Properties

Summary: We report the synthesis, characterisation and photophysical properties of mixed alkyl‐ and alkoxy‐substituted poly[(phenylene ethynylene)‐alt‐(phenylene vinylene)] hybrid polymers with the general constitutional unit: (? Ph? C?C? Ph? C?C? Ph? CH?CH? Ph? CH?CH? )_n ( 7 ). The polymers were obtained through the Horner‐Wadsworth‐Emmons olefination reaction of alkyl‐substituted luminophoric dialdehydes, 5a–b , and alkoxy‐substituted bisphosphonates. Contrary to their alkoxy‐substituted congeners, 10a–b , which exhibit solution fluorescence quantum yields close to unity, dialdehydes ( 5a–b ) fluoresce poorly at room temperature, but show phosphorescence at 77 K. High molecular weight polymers were obtained showing poor solubility compared to solely alkoxy‐substituted polymers ( 11 ) of the same backbone constitutional units. The presence of alkyl side groups in 7 leads to a 15 nm blue shift of their absorption spectra relative to 11 . Both types of polymers show however identical emission spectra with only a slight blue shift (3–4 nm) of the emission peak of 7 relative to 11 . This clearly proves that the chromophore system responsible for the emission in both types of compounds is located around the lower‐energy, alkoxy‐substituted phenylene‐vinylene portion of the polymers as confirmed by fluorescence kinetics investigations.

     

“Click” on Conducting Polymer Coated Electrodes: A Versatile Platform for the Modification of Electrode Surfaces

Two types of N‐substituted pyrroles with azide and terminal alkyne groups have been synthesized and electropolymerized. “Click” chemistry, specifically Huisgen 1,3‐dipolar cycloaddition, was used as a general method for functionalization of the polypyrrole films. Several model compounds, including redox active (quinone), bioactive (cholic acid) and recognition elements (carbohydrate and thymidine) could easily be attached onto the electrode surfaces without loss of functionality or the electroactivity of the underlying conducting polymers. The results suggest that the polypyrrole films are clickable and provide a novel biocompatible and versatile platform for efficient modifications on electrode surfaces.

     

Ammonium‐Functionalized Polydimethylsiloxanes: Synthesis and Properties

Summary: Polydimethylsiloxane with trimethylammonium end groups and polydimethylsiloxane with diethylmethylammonium groups in the main chain was prepared by two routes. A novel carbonate coupler – (2‐oxo‐1,3‐dioxolan‐4‐yl) methyl phenyl carbonate – and the amine compounds α,ω‐(3‐aminopropyl) polydimethylsiloxane, 3‐(dimethylamino)‐1‐propylamine, and bis(2‐amino ethyl)amine served as the starting materials. The polymers obtained are hydrophobic and contain ammonium groups suitable for interaction with negatively charged surfaces. Thus these materials can be used for special surface modifications. Thin films were prepared by spin‐coating. Their morphology and properties were determined by means of optical microscopy, SFM, and contact angle measurements. The particle size distribution in aqueous solution of the vesicles formed was determined by means of a laser scattering technique; the particle sizes determined correspond to those obtained by optical microscopy. Finally, the antibacterial effects of these polymers with hydrophobic and cationic groups were tested.

α,ω‐Diammonium octadimethylsiloxane molecule (6), an SFM phase image for a spin‐coated film of 6 on a silicon wafer, and a scheme of the way the molecules stack on the surface.     

On the Generation of Polyether‐Based Coatings through Photoinduced C,H Insertion Crosslinking

In this work, the synthesis of a photoreactive polyether and its subsequent photochemical attachment to various substrates is described. Poly(bisphenol A‐co‐epichlorohydrin) is chosen as an example for a technologically important class of polymers and modified in a polymeranalogous reaction with photoreactive benzophenone units. During brief UV activation, benzophenone forms reactive intermediates, which are able to formally insert into any aliphatic C,H bond, eventually forming a crosslinked polymer film. During the formation process the emerging polyether networks additionally bind to (practically) any organic molecule present at the substrate surface. This way in one reaction step directly a surface‐attached polymer network is obtained. The examples, which are shown, include silane‐covered oxidic surfaces and unmodified polyolefins. When appropriate masks are used, brief UV irradiation is sufficient to generate crosslinked, surface‐attached polyether microstructures on a broad spectrum of substrate materials. The described strategy allows the generation of one‐component polymer coatings from standard commodity polymers under very simple process conditions, which can be lithographically structured and covalently attached to a broad spectrum of substrates, comprising even chemically rather inert materials.

     

Aliphatic Hyperbranched Copolyesters by Combination of ROP and AB2‐Polycondensation

Summary: Hyperbranched aliphatic copolyesters have been prepared by the copolymerization of ε‐caprolactone and 2,2‐bis(hydroxymethyl)butyric acid (AB₂‐monomer), catalyzed by (i) HfCl₄(THF)₂ and (ii) diphenylammonium trifluoromethanesulfonate (DPAT), respectively. In both cases, copolymerization by combined ROP/AB₂‐polycondensation was achieved. The degree of branching (DB) and consequently the density of functional groups of the resulting copolyesters were controlled by the comonomer ratio in the feed. Molecular weights in the range = 22 000–166 000 g · mol⁻¹ (GPC, PS standards) were obtained, with apparent polydispersity indices of 1.20 to 1.95. The DB was in the range 0.03–0.35. Remarkably, HfCl₄(THF)₂ appeared to cause no transesterification of the ester bonds in the hyperbranched polymer formed. Further esterification or functionalization of the hydroxyl end groups of the hyperbranched polymers is therefore possible in a convenient two step/one pot process. The prepared hyperbranched polycaprolactones can be used as multifunctional initiators for the ROP of ε‐caprolactone, which is also catalyzed by HfCl₄(THF)₂, resulting in multi‐arm star polymers. Diphenylammonium trifluoromethanesulfonate (DPAT) was also found to catalyze the combination of ROP and AB₂ polycondensation. However, the applicability of this system is restricted due to side reactions that can lead to crosslinking.

Synthesis of hyperbranched copolyesters by combined ROP/polycondensation.     

Gel Formation and Molecular Characteristics of Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Redox Polymerization in Aqueous Solution

The molecular characteristics of poly(N‐isopropylacrylamide) (PNIPA), prepared by free‐radical polymerization using an aqueous redox initiator and reaction conditions comparable to those used in the synthesis of nanocomposite gels, were investigated by altering the monomer concentration ([NIPA]) and the polymerization temperature (T_p) across the transition temperature (LCST). When T_p<LCST, there is a critical [NIPA] (=n*) above which PNIPA partially forms gels in the absence of a chemical crosslinker, and the gel fraction increases with increasing [NIPA] and decreasing T_p. In the range of n<n*, the molecular weight of soluble PNIPA correlated well with [NIPA]. When T_p>LCST, gels were not formed regardless of [NIPA]. The structure and mechanism of formation of self‐crosslinked PNIPA gels are discussed.

     

Synthesis and Optical Properties of π‐Conjugated Polymers Composed of Benzo[1,2‐b:4,5‐b′]dithiophene and Thiophenes Bearing Electron‐Deficient Ethenyl Groups in the Side Chains

π‐Conjugated polymers composed of dialkoxybenzo[1,2‐b:4,5‐b′]dithiophene and thiophenes bearing cyano‐alkoxycarbonylethenyl [? CH?C(CO₂R)CN] and bis(alkoxycarbonyl)ethenyl groups [? CH?C(CO₂R)₂] were prepared. The optical properties of the obtained polymers were investigated by UV‐vis and photoluminescence spectroscopy to demonstrate that the absorption maxima of the polymers were tunable by varying the substituent of thiophene unit. The photoluminescence wavelengths and intensities of the polymer in solution were significantly dependent on the polymer side chain. The HOMO energy level of the polymer was lowered by up to ?5.51 eV by introducing electron‐deficient cyano groups. Polymer solar cells based on the new polymers were fabricated to achieve a PCE of 1.90%.

     

Amphiphilic Hyperbranched Polymers Containing Two Types of β‐Cyclodextrin Segments: Synthesis and Properties

Amphiphilic hyperbranched polymers carrying two types of β‐cyclodextrin groups including ionic and covalent bonding were synthesized via atom transfer radical polymerization and immobilization reaction. Their inclusion capabilities for single or double‐guest molecules were investigated by UV‐visible spectroscopy. Using Chlorambucil and Lonidamine as the double model drugs, their encapsulation efficiencies indicate that these polymers possess the capabilities of high drug‐loading. Furthermore, the release behaviors of these polymers were studied via UV‐visible spectroscopy. The results indicate that they can slow the release rate of double model drugs. Varying the pH values of environment or regulating their shell layer structures can control the release behaviors of double model drugs.

     

Helix‐Sense‐Selective Polymerization of Achiral Bis(hydroxymethyl)phenylacetylenes Bearing Alkyl Groups of Different Lengths

4‐Alkyloxy‐3,5‐bis(hydroxymethyl)phenylacetylenes with eight types of alkyl groups were synthesized and polymerized with a chiral catalytic system. We found that the length of the alkyl groups played a very important role in achieving helix‐sense‐selective polymerization. Five helix‐sense‐selective polymerizations were achieved resulting in polymers with alkyl groups whose chain length was longer than six. We think that the longer ‐ chain alkyl groups prevented the polymers from becoming insoluble by forming intermolecular hydrogen bonds between the hydroxyl groups, and stabilized their one‐handed helical structure by promoting the formation of intramolecular hydrogen bonds.