Preparation and Properties of New Soluble π‐Conjugated Polymers Containing a Fumaronitrile Unit in the Main Chain

Summary: A class of new, soluble, π‐conjugated polymers containing a fumaronitrile unit in the main chain were synthesized by the reaction between di(4‐bromophenyl)fumaronitrile and bis(2,2‐dimethylpropane‐1,3‐diyl)‐1,4‐dialkoxyphenylene‐2,5‐diborate employing palladium catalysts. All the polymers were photoluminescent and electrochemically active.

The new soluble π‐conjugated polymers 1a – d with photoluminescence and electrochemical activity synthesized here.     

Spatioselective Modification of Bicompartmental Polymer Particles and Fibers via Huisgen 1,3‐Dipolar Cycloaddition

Precise nano‐ and microscale control of the architecture of biodegradable biomaterials is desirable for several biotechnological applications such as drug delivery, diagnostics, and medical imaging. Herein, we combine electrohydrodynamic co‐jetting and highly specific surface modification (via Huisgen 1,3‐dipolar cycloaddition) to prepare particles and fibers with spatioselective surface modification. We first prepared biphasic particles and fibers from commercial poly(lactide‐co‐glycolide) copolymers via electrohydrodynamic co‐jetting of two organic solutions loaded with fluorescent macromolecules and acetylene‐modified PLGA derivatives. (i) Spatially controlled reaction of poly[lactide‐co‐(propargyl glycolide)] with O‐(2‐aminoethyl)‐O′‐(2‐azidoethyl)heptaethylene glycol and (ii) subsequent conversion of the newly introduced amino groups with fluorescence probes resulted in particles and fibers with surface modification of one hemisphere only.

     

Surface‐Functionalized,Ring‐Opening Metathesis Polymerization‐Derived Monoliths for Anion‐Exchange Chromatography

Ring‐opening metathesis polymerization (ROMP) was used for the synthesis of monolithic capillary columns with inner diameters of 200 µm. The resulting polymeric monoliths were characterized by inverse size‐exclusion chromatography (ISEC). Surface functionalization was carried out in situ using 2‐(N,N‐dimethylaminoethyl)norborn‐5‐ene‐2‐ylcarboxylic amide ( 1 ). The resulting functionalized monoliths were successfully used in anion‐exchange chromatography of oligodeoxynucleotides.

     

Synthesis of Multiblock Polymer Containing Narrow Polydispersity Blocks

Summary: We have developed a new strategy to prepare multiblock polymers and copolymers via one‐ or two‐step polymerization using a polymerizable cyclic trithiocarbonate (CTTC), 4,7‐diphenyl‐[1,3]dithiepane‐2‐thione. CTTC undergoes ring‐opening process to incorporate a trithiocarbonate moiety. The trithiocarbonate moiety in turn, functions as a reversible addition fragmentation chain transfer (RAFT) agent. Through this mechanism, multiblock polystyrenes and polystyrene‐block‐ poly(butyl acrylate) copolymers containing various narrow polydispersity blocks can be prepared.

Integrated process of ring‐opening and RAFT polymerizations involving cyclic trithiocarbonates.     

A Closed‐Loop Phase Diagram in a Weakly Interacting Polyolefin Copolymer Binary Blend System

Summary: The phase behavior of poly(ethylene‐co‐styrene) (PES) and poly(ethylene‐co‐butene) (PEB) blends has been studied. A closed‐loop phase diagram was clearly observed in this weakly interacting system as the styrene content in the PES decreased to about 1 mol‐%. At higher styrene contents, the phase loop starts to interplay with the crystallization transformation at lower temperatures.

Phase diagram of PEB/PES blends. Phase boundary line is only for easy demonstration.     

Synthesis of Poly(ethylene oxide)s Bearing Functional Groups along the Chain

Well‐defined poly(ethylene oxide)s (PEOs) bearing reactive sites regularly distributed along the chain have been synthesized by the polycondensation of PEO containing a central tertiary amino group with dichloromethane, followed by quaternization with suitable reagents to obtain polyzwitterionic or cationic PEOs with alkyl, allyl, or fluorocarbon pendant groups. The pendant allyl groups have been converted into primary amino groups by reaction with 2‐aminoethanethiol hydrochloride to obtain polyamino‐functionalized PEO.

Polyfunctional PEOs bearing different pendant groups.     

Metal Salt‐Induced Ferroelectric Crystalline Phase in Poly(vinylidene fluoride) Films

In this Communication, the effect of varying mass fractions (0–20 wt.‐%) of calcium chloride (CaCl₂) salt on the α‐ and β‐phase content of poly(vinylidene fluoride) (PVDF) as‐cast films were investigated. Spectral and X‐ray studies revealed the maximum ferroelectric β‐phase for the addition of 15 wt.‐% of CaCl₂ in PVDF compared to neat PVDF samples. The dense β‐phase dominant PVDF–CaCl₂ (15 wt.‐%) thick film used as a ferroelectric insulator in one‐capacitor (1C) type random access memory device exhibited a remnant polarization of 3.1 µC · cm², and is a good indication that the unoriented PVDF–CaCl₂ films can be used in electronic applications without further stretching process.

     

Controlled Array of Ferritin in Tubular Nanostructure

We have demonstrated that uniform and continuous poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) (PAMPS) tubular core‐shell nanostructures containing linear features of ferritin nanoparticles can be directly fabricated using two immiscible solutions employing coaxial electrospinning. By adjusting the concentration of PAMPS as the outer solution in the coaxial electrospinning process, the width of a one dimensional (1D) array of ferritin could be accurately controlled. We demonstrate the formation of a nearly linear chain of individual ferritin particles encapsulated in a PAMPS nanofiber of 40 nm diameter. The ability to accurately control the width of the ferritin 1D arrays encapsulated in tubular nanostructures is a key component in determining the efficiency and performance of nanodevices. The demonstrated method of forming tubular nanostructures containing inner 1D particle arrays can also be extended to other materials with potential applications in nanoelectronic devices, such as nanobiosensors and batteries.

     

Multicomponent Phase Change Microfibers Prepared by Temperature Control Multifluidic Electrospinning

Multicomponent phase change microfibers, which can storage and release thermal energy in a stepwise manner, are firstly prepared through a facile one‐step multifluidic compound‐jet electrospinning with temperature control. The multiresponsive effect benefits from a special multichannel tubular microstructure that could controllably encapsulate different phase change materials into the channels independently. Aside from the fabrication of multicomponent phase change microfibers, the melt multifluidic compound‐jet electrospinning is promising for applications related to microencapsulation and multifunctional material fields.

     

Crystal Orientation Behavior of a Poly(vinylidene fluoride)/Nylon 11 Blend

The oriented crystallization of poly(vinylidene fluoride) (PVDF) in stretched films of a PVDF/nylon 11 blend was investigated. At low crystallization temperature the c‐axis of the PVDF α‐form was oriented to the orientation axis of the nylon 11 matrix, but c‐axis orientation gradually changed to a‐axis orientation upon increasing the crystallization temperature. Under all crystallization conditions studied, considerable amounts of PVDF in its β‐form with c‐axis orientation were produced as well.

Phase morphology of a stretched film of PVDF/nylon 11 blend observed with confocal laser scanning microscopy.     

Selective and Sequential Re‐Assembly of Patterned Block Copolymer Thin Film for Fabricating Polymeric,Inorganic, and Their Composite Nanostructured Arrays

We report that the nanostructures of poly(styrene‐block‐4‐vinylpyridine) block copolymer (PS‐b‐P4VP) thin film on a wafer substrate can be re‐assembled by sequential vapor treatment using selected solvents. Metal or other inorganic nanoparticles that were randomly pre‐loaded inside or on the surface of PS‐b‐P4VP thin film could be pulled to the rim of PS and P4VP along with the movements of PS and P4VP blocks during the treatment. As a result, the patterned polymeric or inorganic/polymer composite nanoisland and nanoring arrays were fabricated.

     

Superelectrophilic Activation of N‐Substituted Isatins: Implications for Polymer Synthesis,a Theoretical Study

The stability and reactivity of mono‐ and multi‐protonatred N‐substituted isatin derivatives were studied at PBE0/aug‐cc‐pvtz//PBE0/6‐31+G** level of theory in triflic acid (TFSA) solution. Calculations showed that the monocationic intermediates are the principal reactive species in the reaction of hydroxyalkylation of isatin derivatives in TFSA media. Electron‐withdrawing substituents on the nitrogen atom increase the reactivity of isatin‐containing electrophiles towards aromatic hydrocarbons, in accordance with their expected electronic influence. Steric factors also play an important role in the reactivity of isatin‐containing electrophiles, especially in the second reaction step, due to their more sterically hindered reactive center.

     

Construction of Glycosylated Surfaces for Poly(propylene) Beads with a Photoinduced Grafting/Chemical Reaction Sequence

Surface modification of commercial PPBs with different saccharides is described. Surface‐glycosylated PPBs were prepared through reaction between the hydroxyl groups of poly(HEMA) and acetylated saccharides such as α‐glucose pentaacetate, β‐galactose pentaacetate, and lactose octaacetate. The modified PPBs were characterized by XPS and water contact angle measurement. It was found that the grafting degree of poly(HEMA) increases with UV irradiation time, monomer concentration, and water content in solvent. The binding degree of monosaccharides is higher than that of disaccharides. The glycosylated PPBs can selectively recognize lectins, indicating potential for protein isolation.

     

Well‐aligned Nano‐fiberous Membranes Based on Three‐pole Electrospinning with Channel Electrode

Three‐pole electrospinning devices integrated with a blade‐cage collector were developed to fabricate well‐aligned nano‐fiberous membranes. The proposed three‐pole configuration with a channel electrode can be a powerful tool in aligning nano‐fibers with regular diameter because the generated electric field can be accurately controlled without severe fluctuation in comparison with other methods. The three‐pole electrospinning method is also valid for industrial mass production and accurate diameter control of the aligned nano‐fibers.

     

Preparation of Antimicrobial Ultrafine Cellulose Acetate Fibers with Silver Nanoparticles

Summary: A feasible method for the preparation of antimicrobial ultrafine fibers with silver nanoparticles was developed by direct electrospinning of a cellulose acetate (CA) solution with small amounts of silver nitrate followed by photoreduction. Silver nanoparticles in ultrafine CA fibers were stabilized by interactions with carbonyl oxygen atoms in CA. Ultrafine CA fibers with silver nanoparticles showed very strong antimicrobial activity.

TEM image of an ultrafine CA fiber electrospun from 10 wt.‐% CA solution with 0.5 wt.‐% AgNO₃.     

Mechanistic Investigation into the Unique Orientation Textures of Poly(vinylidene fluoride) in Blends with Nylon 11

Self‐seeded crystallization experiments were carried out to detect the mechanism of the unique orientation behavior of poly(vinylidene fluoride) (PVDF) in oriented PVDF/nylon 11 blends. It was found that primary nuclei have no effects on the final orientation textures adopted by PVDF. The results show that the PVDF crystal orientation in the oriented blends is determined in the early stage of crystal growth, thus a trans crystallization mechanism is preferred.

Isothermal crystallization kinetics for the self‐seeded and non‐self‐seeded crystallization at 145 °C.     

RAFT Inverse Miniemulsion Polymerization of Acrylamide

RAFT inverse miniemulsion polymerization is demonstrated for the first time as an alternate way to synthesize hydrophilic polymer latexes. The kinetic behavior of inverse RAFT miniemulsion polymerization of acrylamide is similar to that observed in aqueous RAFT solution polymerization. A water‐soluble initiator provides better control than a lipophilic initiator in inverse RAFT miniemulsion polymerization under the conditions used here.

     

Poly(dicyclopentadiene) Submicron Fibers Produced by Electrospinning

Summary: We have used the process of electrospinning to produce fibers of poly(dicyclopentadiene) with diameters on the submicron scale. The material, formed from a monomer‐catalyst solution, polymerized in flight during the electrospinning process. Fibers were collected over trenches etched in silicon and the Young's moduli were measured using an atomic force microscope to measure force‐displacement curves. The resulting values of Young's moduli are larger than typical values for bulk polymer material.

SEM image of suspended PDCPD fiber.     

Influence of Copolymerization on Fragmentation Behavior Using Ziegler‐Natta Catalysts

Summary: A morphological investigation was carried out on different Ziegler‐Natta catalysts during the early stages of propylene homo‐ and propylene‐ethylene copolymerization. For similar polymerization conditions, but dependent on the nature of the catalysts, fragmentation occurs layer‐by‐layer or instantaneously into a large amount of small pieces. However, the incorporation of comonomer ethylene slows down the fragmentation progress. This is believed to be the result of the higher mobility of the just formed propylene‐ethylene copolymer molecules at the active sites.

SEM images of the cross‐sectional morphology of polymer particles from catalyst‐I.