New Poly(propylene glycol)‐ and Poly(ethylene glycol)‐Based Polymer Gelators with L‐Lysine

Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L ‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.

Structures of the polymer gelators synthesized here.     

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.     

Hydrodynamic Effect on Secondary Phase Separation in an Epoxy Resin Modified with Polyethersulfone

Summary: The evolution of the morphologies in blends of epoxy/4,4′‐methylenebis(2,6‐dimethylaniline)/polyethersulfone was followed by time‐resolved light scattering, optical microscopy and scanning electron microscopy. The results suggest that, once the diffusion of epoxy molecules cannot follow the geometrical growth, a secondary phase separation occurs, even in the droplet morphology, in which the size of the epoxy‐rich domain grows as usual. The viscoelastic effect of polyethersulfone is also discussed.

Development of morphologies followed by OM: bicontinuous phase separation in the PES‐15.9 blend cured at 140 °C after 80 s.     

Facile Fabrication of Functional Polypyrrole Nanotubes via a Reactive Self‐Degraded Template

Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in‐situ polymerization. During the process fibrillar complex of FeCl₃ and methyl orange (MO), acting as a reactive self‐degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.

TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min.     

Biocompatible Micelles Based on Comb‐like PEG Derivates: Formation,Characterization, and Photo‐responsiveness

A novel comb‐like derivative CPEG‐g‐DNQ was prepared by incorporating light responsive 2‐diazo‐1,2‐naphthoquinone (DNQ) groups into the structure of comb‐like poly(ethylene glycol) (CPEG). DLS and TEM results showed that CPEG‐g‐DNQ self‐assembled into spherical micelles with an average size of about 135 nm in water. Upon exposure to light, the micelles could be disrupted because of the conversion of hydrophobic DNQ to hydrophilic 3‐indenecarboylic acid. Additionally, hydrophobic coumarin 102 was successfully loaded into the micelles and photo‐induced ON‐OFF release was demonstrated by fluorescence spectroscopy. MTT assay revealed that the micelles are biocompatible. These photo‐responsive micelles might have great potential for controlled release of hydrophobic drugs.

     

A Rapid Eco‐Friendly Synthesis of Poly(butylene succinate) by a Direct Polyesterification under Microwave Irradiation

Summary: A rapid and eco‐friendly synthesis of poly(butylene succinate) (PBS) using microwaves was developed in the presence of 1,3‐dichloro‐1,1,3,3‐tetrabutyldistannoxane as catalyst. To determine the optimum conditions, the effect of catalyst concentration, bulk vs. solution polymerization, reaction time, temperature, and stoichiometry of the monomers were studied. Based on the optimum conditions, PBS with a weight‐average molecular weight of 2.35 × 10⁴ was obtained in a short time of 20 min.

Synthesis of poly(butylene succinate) under microwave irradiation.     

Kinetics Approximation Considering Different Reactivities of the Structural Units Formed by the Anionic Copolymerization of 1,3‐Butadiene and Styrene Using Al/Li/Ba as Initiator

The copolymerization reaction of butadiene and styrene copolymers prepared by anionic living polymerization using an initiator composed of alkyl aluminum, n‐butyl lithium, and barium alkoxide is studied using a kinetic model that considers the reactivity of active sites to be different; this assumption is justified by the varying geometric configurations. With the first‐order Markov model, the expressions for the fraction of active sites and dyad distribution are obtained. The rate constants are determined by fitting to the conversion and Bernoulli dyad data using the nonlinear least squares method. The conversion and dyad sequence distribution are correctly predicted, and the experimental results indicate that the microstructure and sequence distribution do not change with the conversion and temperature.

     

Improved PEDOT Conductivity via Suppression of Crystallite Formation in Fe(III) Tosylate During Vapor Phase Polymerization

Vapor phase polymerization was used to synthesize high conductivity poly(3,4‐ethylenedioxyphenylene) (PEDOT). The monomer is presented to an oxidant‐rich substrate in vapor form and even for short polymerization times, 10–30 min, Fe(III) tosylate has a propensity for water absorption leading to crystal formation. Poor oxidant treatment before polymerization or high humidity during polymerization can create holes in the PEDOT film decreasing its conductivity. The addition of an amphiphilic copolymer poly(ethylene glycol)‐ran‐poly(propylene glycol) suppresses crystal growth allowing better film formation. The humidity level during synthesis was optimized at 35% relative humidity (RH), producing a conductivity of 761 S · cm⁻¹. Additionally, the copolymer extends the RH range that is tolerable for polymer synthesis.

     

Modification of Polymer Substrates with Low Surface Free Energy Material by Low‐Temperature Cured Polybenzoxazine

The B‐ala/AIBN PBZ system has a high extent of ring‐opening of oxazine because phenol‐containing oligomers are formed at the early stage of the curing process. As a result, the B‐ala/AIBN PBZ system possesses a relatively stronger intramolecular hydrogen bonding and lower surface energy than the pure B‐ala system at low temperature curing. In this context, poly(4‐vinyl pyridine), poly(4‐vinyl phenol) thin films and polycarbonate substrates, which lack liquid resistance, possess low surface free energy after modification with B‐ala/AIBN = 5/1 PBZ.

     

Macromonomer Purification Strategy for Well‐Defined Polymer Amphiphiles Incorporating Poly(ethylene glycol) Monomethacrylate

Summary: Commercial hydroxy‐terminated poly(ethylene glycol) monomethacrylates (PEG‐MAs) contain poly(ethylene glycol) dimethacrylate, which leads to unfavorable gel formation on polymerization. Here, hydroxy‐terminated PEG‐MA is readily isolated using a dimethylsilyl resin chlorinated with 1,3‐dichloro‐5,5‐dimethylhydantoin. Solution polymerization of the isolated PEG‐MA by free radical routes gives a high‐molecular‐weight amphiphilic graft copolymer without cross‐linking. The resulting polymer is stable for long periods in ambient conditions with preservation of the hydroxy end groups of PEG.

Commercial hydroxy‐terminated PEG‐MA can be separated readily and completely from PEG dimethacrylate contaminant with chlorinated dimethylsilyl resin.     

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.

     

Electro‐Copolymerization of Layer‐by‐Layer Deposited Polythiophene and Polycarbazole Precursor Ultrathin Films

The synthesis, layer‐by‐layer deposition, and electro‐copolymerization of precursor polyelectrolyte multilayer ultrathin films with thiophene and carbazole electroactive groups are described. The interest is in observing an electrochemical cross‐linking approach towards a highly ordered ultrathin film that contains two types of monomers to result in possible layer‐limited homo‐ and copolymerization. A uniform linear growth with alternate deposition of the polyelectrolytes is observed. The multilayer films were then electrochemically polymerized anodically by cyclic voltammetry (CV), which results in copolymerization between two different electroactive groups. Cross‐linking of the layers was verified by CV and spectroelectrochemistry data with very good linear electro‐copolymerizability.

     

Observations on Solution Crystallization of Poly(vinyl alcohol) in the Presence of Single‐Wall Carbon Nanotubes

PVA/SWNT dispersions yield aloe plant‐like crystals, where the leaves are single crystals templated by PVA coated SWNT. Longer growth times (≈18 months) lead to hexagonal rod‐like crystals. HR‐TEM images show evidence that PVA molecules are aligned parallel to the SWNT axis. WAXD, electron diffraction, and HR‐TEM observations of these aloe plant and hexagonal crystals suggests evidence for possible PVA‐SWNT epitaxy. Wide‐angle and electron diffraction data of these crystals also show that the structure seems to mimic the 2D hexagonal crystal packing of SWNT. PVA lattice images and moiré fringes were also observed in the leaf‐like crystals.

     

Effect of Free Trimethylaluminum Content in Methylaluminoxane on Performances of Bis(salicylaldiminate)nickel(II)‐Based Catalysts for Ethylene Polymerization

Summary: The performances of ethylene polymerization catalysts based on III and commercial methylaluminoxane were investigated by reducing the content of free trimethylaluminum in methylaluminoxane by its reaction with 2,6‐di‐tert‐butylphenol. This allowed optimization of the formulation of the catalyst, affording a high‐molecular‐weight linear polyethylene (PE) with a productivity [(1 900 kg of PE/(mol of Ni × h)], ten‐fold higher than that previously achieved for the same system adopting commercial methylaluminoxane not pre‐treated with the above phenol derivative.

     

A Mixed Ruthenium Polypyridyl Complex Containing a PEG‐Bipyridine Macroligand

Summary: An amino‐functionalized bipyridine ligand was prepared in order to serve as a bridging unit to an activated low‐molecular‐weight monomethyl ether of poly(ethylene glycol) (PEG). Coordination of a ruthenium(II ) phenantroline precursor onto the formed PEG‐containing bipyridine ligand yielded a metal‐containing polymer which shows interesting properties for solar cell applications.

A schematic of the described polymeric ruthenium(II ) complex and its absorption and emission properties.     

Square Lamellar Structure Having Phase‐Separated Microdomain in H‐Shaped Block Copolymer Thin Film

The morphology of a H‐shaped block copolymer (poly(ethylene glycol) backbone and polystyrene branches (PS)₂PEG(PS)₂) in a thin film has been investigated. A peculiar square lamella that has a phase‐separated microdomain at its surface is obtained after spin coating. The experimental temperature plays a critical role in the lamellar formation. The copolymer first self‐assembles into square lamellar micelles with an incomplete crystalline core due to the crystallizability of PEG. In the subsequent process of solvent evaporation, phase separation between PS and non‐crystalline PEG attached at the chain‐folded PEG surface takes place, which results in phase‐separated microdomains being formed at the lamellar surface.

     

Novel Biodegradable Copolymers with a Periodic Sequence Structure Derived from Succinate Butan‐1,4‐diol,and Butan‐1,4‐diamine

Summary: Novel biodegradable copolymers derived from succinate, butan‐1,4‐diol, and butan‐1,4‐diamine were synthesized by two‐step polycondensation reactions. The obtained copolymers had a periodical‐sequence structure consisting of ester and amide units, and the melting temperatures of the periodic copolymers increased with an increase in amide content. The crystalline structure of the periodic copolymers differs from that of butylene succinate homopolymer (PBS), and these results suggest that the periodically introduced amide units are included in the crystalline phase forming a novel crystalline structure.

Periodic copolyester‐amides derived from succinate, butane‐1,4‐diol, and butan‐1,4‐diamine     

Mild Synthesis of Amino‐Poly(ethylene glycol)s. Application to Steric Stabilization of Clays

The hydroxyl end groups of poly(ethylene glycol) (PEG) have been transformed easily and quantitatively into amino groups via the Mitsunobu reaction. Phthalimide was alkylated with PEGs and the hydrazinolysis of the resulting phthalimido‐PEGs gave the amino compounds in high yields. Quaternization of the amino groups leads to hydrophilic polymer chains bearing a positive charge on one or two ends, depending on the chosen PEG. Such products can be used to protect sterically, negatively charged particles such as clays.

     

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.