Mapping Acid‐Catalyzed Deprotection in Thin Polymer Films: Fluorescence Imaging Using Prefluorescent 7‐Hydroxycoumarin Probes

Summary: Fluorescent images that illustrate acid‐catalyzed tert‐butoxycarbonyl (tBoc) deprotection patterns in polymer films were obtained using fluorescent sensors based on 7‐hydroxycoumarin dyes. Three commercial 7‐hydroxycoumarins, which are highly fluorescent, become practically nonemissive upon protection of the 7‐hydroxyl position with tBoc. In thin polymer films, the protected “prefluorescent” probes can return to their deprotected, fluorescent states by reaction with catalytic amounts of photogenerated acid and mild heating.

Protected probes become highly fluorescent after acid‐induced deprotection.     

Soluble Polyimides from a New Dianhydride: 5′‐tert‐Butyl‐m‐terphenyl‐3,4,3″,4″‐tetracarboxylic Acid Dianhydride

A novel tert‐butyl‐containing dianhydride was prepared from readily available reagents. It was reacted with various aromatic diamines to prepare a set of polyimides containing tert‐butyl pendent groups. The resulting polyimides exhibit high molecular weights (high inherent viscosity), and a combination of desirable properties, such as good solubility in aprotic amide solvents and cresols, high glass transition temperatures (up to 320 °C), high thermal resistance, film‐forming capability and good mechanical properties.

     

Lewis Acid‐Induced N‐Methyleneamines as Initiators in the Synthesis of Secondary Amine‐Terminated Polymers

Summary: The cationic polymerization of poly(tert‐butyl vinyl ether) using N‐methyleneamine equivalents derived from a Lewis acid/1,3,5‐trimethylhexahydro‐1,3,5‐triazine (TMTA) co‐initiating system is reported. The resulting polymers possessed secondary amine functionality at the chain terminus, verified by derivatization with 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl) and subsequent analysis with GPC‐UV (470 nm) and ¹H NMR.

Use of N‐methyleneamine equivalents lacking aryl substituents to afford amine‐terminated poly(tert‐butyl vinyl ether).     

A New Route for the Modification of Halogen End Groups to Amino End‐Functionalized Poly(tert‐butyl acrylate)s

The synthesis of primary amine end‐functional poly(tert‐butyl acrylate)s has been achieved by using the Gabriel reaction. Polymerization of tert‐butyl acrylate was first achieved by atom transfer radical polymerization using ethyl‐2‐bromoisobutyrate or paramethoxyphenyl‐2‐bromoisobutyrate as initiator. Both resulting polymers, with a bromide‐end atom, were converted into phthalimido intermediates which then were successfully hydrolyzed using potassium hydroxide in tert‐butyl alcohol to result in poly(tert‐butyl acrylate)s terminated by a primary amine function. End group interconversions were followed by ¹H NMR, FT‐IR, and MALDI‐TOF MS measurements. All the results proved that quantitative transformations were achieved at each step. Moreover, the method developed is very easy to carry out.

     

Multicomb Polymeric Supramolecules and Their Self‐Organization: Combination of Coordination and Ionic Interactions

Several alkyl side chains are bonded to each polymeric repeat unit using both coordinated ligands and electrostatically bound counterions to directly control the interface curvature of the self‐organized structures. 2,6‐Bis(octylaminomethyl)pyridine is Zn‐coordinated to poly(4‐vinylpyridine) (P4VP) with dodecylbenzenesulfonate (DBS) counterions, leading to multicomb polymeric supramolecules, poly[(4VP)Zn(2,6‐bis(octylaminomethyl)pyridine)(DBS)₂]. Coordination is evidenced by infrared spectroscopy and visualized by quantum chemical calculations. The amorphous hexagonal self‐organized structures are characterized using X‐ray measurements.

     

Dual Self‐Assembling Polycondensation of p‐Acetoxybenzoic Acid and p‐Acetamidobenzoic Acid

The dual self‐assembling polycondensation of p‐acetoxybenzoic acid (ABA) and p‐acetamidobenzoic acid in Therm S 800 was examined at 300 °C. Needle‐like crystals and lath‐like crystals were formed simultaneously through reaction‐induced crystallization of oligomers at a molar ratio of 30–50 mol‐% ABA in the feed. The needle‐like crystals comprised more p‐oxybenzoyl units, whereas the lath‐like ones contained higher amounts of p‐benzamide moieties.

     

Synthesis and Surface Morphology of Tetraaniline‐block‐Poly(L‐lactate) Diblock Oligomers

Summary: Tetraaniline‐block‐poly(L ‐lactide) diblock oligomers are synthesized via ring‐opening polymerization. The diblock oligomers cast from an L ‐lactide selective solvent (chloroform) show spherical aggregates for the leucoemeraldine state, and ring‐like structures that are composed of much smaller spherical aggregates for the emeraldine state. The formation mechanisms of the two different surface morphologies are discussed in detail.

Surface morphology changes induced by oxidation of the aniline segment of tetraaniline‐block‐poly(L ‐lactate) and drying effects.     

Supramolecular Dynamics as Origin for Thermally Induced Insoluble‐to‐Soluble‐to‐Insoluble Transitions of Copolymers in Water

The synthesis of cationic mono‐(6‐O‐(1‐vinylimidazolium))‐ß‐cyclodextrin with toluenesulfonate as the corresponding anion is described. Free‐radical copolymerization of the resulting host–guest complex with N‐isopropylacrylamide or N,N‐diethylacrylamide yielded copolymers showing a temperature‐controlled solubility window in water. The impact of different anionic guests and salt concentrations on solubility behavior was investigated via turbidity measurements.

     

Supramolecular Gels Based on Multi‐Walled Carbon Nanotubes Bearing Covalently Attached Cyclodextrin and Water‐Soluble Guest Polymers

The preparation of associative networks containing multi‐walled carbon nanotubes (MWCNTs) with covalently attached cyclodextrin (CD) rings and poly[(isobutylene)‐co‐(maleic anhydride)‐co‐(maleic acid‐(4‐tert‐butylphenyl)amide)] in water is described in this study. The synthesis of CD containing MWCNTs is realized by an amidation reaction of oxidized MWCNTs with propargylamine followed by a 1,3‐dipolar cycloaddition with CD‐azide. Dispersion behavior indicated the high stability of these networks. An increase in viscosity compared to a solution of pure polymer as a cause of network formation is observed. The addition of a CD‐decomposing enzyme (taka‐diastase from Aspergillus oryzae) let the network collapse and results in sedimentation of the modified MWCNTs.

     

Solvent Vapor‐Induced Nanowire Formation in Poly(3‐hexylthiophene) Thin Films

Summary: Nanowire lengths and length‐to‐width aspect ratios in regioregular poly(3‐hexylthiophene) (P3HT) were simply controlled through changes in the solvent vapor pressure during solidification. It is demonstrated that the nanowires grew by rod‐to‐rod association, in which the molecular long axis of the P3HT chains appeared to be well‐oriented parallel to the silicon substrate (Si/SiO_x). The formation of the nanowires took place by one dimensional self‐assembly, governed by π‐π stacking of the P3HT units.

TEM high contrast images showing P3HT nanowires fabricated by spin‐coating under a solvent vapor pressure.     

Step‐Growth Radical Addition‐Coupling Polymerization (RACP) for Synthesis of Alternating Copolymers

We report a new type of step‐growth radical addition‐coupling polymerization (RACP) involving consecutive addition of carbon‐centered radical derived from α,α′‐dibromo dibasic ester to NO double bond of C‐nitroso compound followed by cross‐coupling of carbon‐centered radical and in situ formed nitroxyl radical, which produces alternating copolymers with high molecular weight and unimodal molecular weight distribution from saturated and unsaturated monomers.

     

A Self‐Assembling Polythiophene Functionalised with a Cysteine Moiety

A new copolymer bearing a cysteine moiety, designed for molecular interaction, metal‐ion detection, and chiral recognition, was synthesised starting from the dibromo derivative of methyl N‐(tert‐butoxycarbonyl)‐S‐thien‐3‐ylcysteinate and distannylthiophene through a Stille coupling reaction. UV‐vis spectroscopy, circular dichroism, NMR spectroscopy, and gel permeation chromatography analyses evidenced that this polymer is able to form self‐assembling structures, through the formation of a hydrogen‐bond network, not only in the solid state but also in solution.

     

Conjugated Microporous Networks on the Basis of 2,3,5,6‐Tetraarylated Diketopyrrolo[3,4‐c]pyrrole

π‐Conjugated microporous networks have been prepared from the tetraarylated diketopyrrolo[3,4‐c]pyrrole unit as a tetrafunctional building block. The reactions are carried out using microwave‐assisted Yamamoto or Sonogashira cross‐coupling. Red insoluble powders are obtained, showing intense fluorescence. The polymer networks exhibit a high gas storage capability, with BET surface areas up to about 500 m² · g⁻¹.