A Novel ABC Triblock Copolymer with Very Low Surface Energy: Poly(dimethylsiloxane)‐block‐Poly(methyl methacrylate)‐block‐Poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate)

Poly(dimethylsiloxane)‐block‐poly(methyl methacrylate)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) was successfully synthesized via ATRP. The chemical composition and structure of the copolymer was characterized by NMR and FT‐IR spectroscopy and molecular weight measurement. Gel permeation chromatography was used to study the molecular weight distribution of the triblock copolymer. The surface properties of the resulting copolymer were investigated. The effects of fluorine content and bulk structure on surface energy were investigated by static water contact angle measurements. Surface composition was studied by XPS.

     

Fabrication of Poly(L‐lactide)‐block‐Poly(ethylene glycol)‐block‐Poly(L‐lactide) Triblock Copolymer Thin Films with Nanochannels: An AFM Study

This paper aims to report the fabrication of biodegradable thin films with micro‐domains of cylindrical nanochannels through the solvent‐induced microphase separation of poly(L ‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(L ‐lactide) (PLA‐b‐PEG‐b‐PLA) triblock copolymers with different block ratios. In our experimental scope, an increase in each of the block lengths of the PLA and PEG blocks led to both a variation in the average number density (146 to 32 per 100 µm²) and the size of the micro‐domains (140 to 427 nm). Analyses by atomic force microscopy (AFM) and fluorescence microscopy indicated that the hydrophilic PEG nanochannels were dispersed in the PLA matrix of the PLA‐b‐PEG‐b‐PLA films. We demonstrated that the micro‐domain morphology could be controlled not only by the block length of PEG, but also by the solvent evaporation conditions.

     

Electrosynthesis and Characterization of Poly(N‐(9‐fluorenylmethoxycarbony)‐glycine)

High‐quality poly(N‐(9‐fluorenylmethoxycarbony)‐glycine) (PFG), a new kind of soluble polyfluorene derivative, was successfully synthesized electrochemically by direct anodic oxidation of N‐(9‐fluorenylmethoxycarbony)‐glycine (FG) in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of FG in BFEE was only 0.6 V vs. Pt, which was much lower than that in acetonitrile +0.1 mol/L tetrabutylammonium tetra?uoroborate (TBATFB). PFG film obtained from BFEE showed good electrochemical activity and thermal stability. It indicates that BFEE is a better medium for the electrosynthesis of PFG film. PFG is highly soluble in common organic solvents, facilitating potential applications as a blue‐light‐emitting material. Fluorescent spectra revealed that PFG was a good blue‐light emitter. Results of FT‐IR and ¹H NMR spectra indicated the polymerization location of N‐(9‐fluorenylmethoxycarbony)‐glycine occurred mainly at C(2) and C(7) positions of the fluorine ring.     

Self‐Assembly of Poly(γ‐benzyl L‐glutamate)‐graft‐Poly(ethylene glycol) and Its Mixtures with Poly(γ‐benzyl L‐glutamate) Homopolymer

Summary: Self‐association behaviors of poly(γ‐benzyl L ‐glutamate)‐graft‐poly(ethylene glycol) (PBLG‐graft‐PEG) and its mixtures with PBLG homopolymer in aqueous media were investigated by fluorescence spectroscopy, transmission electron microscopy (TEM), and nuclear magnetic resonance (NMR) spectroscopy. It was revealed that PBLG‐graft‐PEG could self‐assemble to form polymeric micelles with a core‐shell structure in the shape of spindle. The introduction of PBLG homopolymer not only decreases the critical micelle concentration, but also changes the morphology of the micelles.

The excitation fluorescence spectra of pyrene as a function of concentrations for the mixture of PBLG‐graft‐PEG with PBLG and a TEM image of the formed micelles.     

Synthesis and Characterization of a Block Copolymer Containing Regioregular Poly(3‐hexylthiophene) and Poly(γ‐benzyl‐L‐glutamate)

Poly(3‐hexylthiophene)‐b‐poly(γ‐benzyl‐L ‐glutamate) (P3HT‐b‐PBLG) rod–rod diblock copolymer was synthesized by a ring‐opening polymerization of γ‐benzyl‐L ‐glutamate‐N‐carboxyanhydride using a benzylamine‐terminated regioregular P3HT macroinitiator. The opto‐electronic properties of the diblock copolymer have been investigated. The P3HT precursor and the P3HT‐b‐PBLG have similar UV–Vis spectra both in solution and solid state, indicating that the presence of PBLG block does not decrease the effective conjugation length of the semiconducting polythiophene segment. The copolymer displays solvatochromic behavior in THF/water mixtures. The morphology of the diblock copolymer depends upon the solvent used for film casting and annealing results in morphological changes for both films deposited from chloroform and trichlorobenzene.

     

Thermoresponsive Poly(2‐oxazine)s

The monomers 2‐methyl‐2‐oxazine (MeOZI), 2‐ethyl‐2‐oxazine (EtOZI), and 2‐n‐propyl‐2‐oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring‐opening polymerization (CROP) under microwave‐assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting LCST behavior in water and their cloud point temperatures (T_CP) are lower than for poly(2‐oxazoline)s with similar side chains. However, comparison of poly(2‐oxazine) and poly(2‐oxazoline)s isomers reveals that poly(2‐oxazine)s are more water soluble, indicating that the side chain has a stronger impact on polymer solubility than the main chain. In conclusion, variations of both the side chains and the main chains of the poly(cyclic imino ether)s resulted in a series of distinct homopolymers with tunable T_CP.     

Triblock Copolymer Based on Poly(propylene oxide) and Poly(1‐[11‐acryloylundecyl]‐3‐methyl‐imidazolium bromide)

The controlled atom transfer radical polymerization of an ionic liquid, 1‐(11‐acryloylundecyl)‐3‐methyl imidazolium bromide (ILBr), from both ends of a telechelic poly(propylene oxide) (PPO) macroinitiator, end‐functionalized with bromoisobutyryloyl is reported. The resulting highly water‐soluble triblock, poly(ILBr‐b‐PO‐b‐ILBr) is multistimuli responsive. This new class of triblocks exhibits classical surface activity in lowering surface tension at the air–water interface and in modifying wetting in waterborne coatings. It also immunizes model colloids against coagulation induced by Debye–Hückel (indifferent electrolyte) electrostatic screening. Further, sol–gel thermoreversibility is unexpectedly found as an additional form of stimuli responsiveness.     

Synthesis of Poly(glycidyl methacrylate)‐block‐Poly(pentafluorostyrene) by RAFT: Precursor to Novel Amphiphilic Poly(glyceryl methacrylate)‐block‐Poly(pentafluorostyrene)

Poly(glycidyl methacrylate) (PGMA) was synthesized by the RAFT method in the presence of 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) chain transfer agent using different [GMA]/[CPDB] molar ratios. The living radical polymerization resulted in controlled molecular weights and narrow polydispersity indices (PDI) of ≈1.1. The polymerization of pentafluorostyrene (PFS) with PGMA as the macro‐RAFT agent yielded narrow PDIs of ≤1.2 at 60 °C and ≤1.5 at 80 °C. The epoxy groups of the PGMA block were hydrolyzed to obtain novel amphiphilic copolymer, poly(glyceryl methacrylate)‐block‐poly(pentafluorostyrene) [PGMA(OH)‐b‐PPFS]. The PGMA epoxy group hydrolysis was confirmed by ¹H NMR and FTIR spectroscopy. DSC investigation revealed that the PGMA‐b‐PPFS polymer was amorphous while the PGMA(OH)‐b‐PPFS displayed a high degree of crystallinity.

     

CO2‐ and O2‐Sensitive Fluorophenyl End‐Capped Poly(ethylene glycol)

Pentafluorophenyl end‐capped poly(ethylene glycol) (PF‐PEG‐PF) aqueous solution shows a lower critical solution temperature (LCST), which is sensitive to the type of gases dissolved in the solution. LCST increases from 24.5 to 26 °C when dissolved carbon dioxide is replaced by oxygen. The transparent‐to‐turbid transition is reversibly observed when the dissolved carbon dioxide in the PF‐PEG‐PF aqueous solution is exchanged with oxygen, and vice versa, at 24.5 °C. ¹⁹F NMR and ¹H NMR spectra of the PF‐PEG‐PF in D₂O suggest that 1) dehydration of PEG is the main reason of developing LCST of the PF‐PEG‐PF aqueous solution, 2) minute differences in the intermolecular interactions, as demonstrated by changes in the chemical shift of the PF‐PEG‐PF peaks, induce such a difference in LCST. This paper provides a new insight in designing a stimuli‐responsive polymer in that fine tuning of a phase transition can be controlled by the type of dissolved gas.

     

Poly(ε‐caprolactone)‐Based Organogels and Hydrogels with Poly(ethylene glycol) Cross‐Linkings

Summary: The reaction of triphosgene with poly(ethylene glycol) yielded poly(ethylene glycol) dichloroformate. This difunctional cross‐linker was allowed to react with poly(ε‐caprolactone) bearing carbanionic sites obtained by activation with lithium diisopropylamide. The reaction resulted in the cross‐linking of poly(ε‐caprolactone) chains by poly(ethylene glycol) segments, giving copolymer networks that gel in both organic and aqueous media.

Schematic of the PCL‐g‐PEG copolymers synthesized here.     

Novel Amphiphilic Degradable Poly(ε‐caprolactone)‐graft‐poly(4‐vinyl pyridine), Poly(ε‐caprolactone)‐graft‐poly(dimethylaminoethyl methacrylate) and Water‐Soluble Derivatives

New amphiphilic graft copolymers that have a poly(ε‐caprolactone) (PCL) biodegradable hydrophobic backbone and poly(4‐vinylpyridine) (P4VP) or poly(2‐(N,N‐dimethylamino)ethyl methacrylate) (PDMAEMA) hydrophilic side chains have been prepared by anionic polymerization of the corresponding 4VP and DMAEMA monomers using a PCL‐based macropolycarbanion as initiator. The water solubility of these amphiphilic copolymers is improved by quaternization, which leads to fully water‐soluble cationic copolymers that give micellar aggregates in deionized water with diameters ranging from 65 to 125 nm. In addition, to improve the hydrophilicity of PCL‐g‐P4VP, grafting of poly(ethylene glycol) (PEG) segments has been carried out to give a water‐soluble double grafted PCL‐g‐(P4VP;PEG) terpolymer.

     

Multi‐Morphological Complex Aggregates Formed from Amphiphilic Poly(ethylene oxide)‐block‐Polydimethylsiloxane‐block‐Poly(ethylene oxide) Triblock Copolymers

Summary: Amphiphilic triblock copolymers (PEO_x‐b‐PDMS_y‐b‐PEO_x) with different block lengths were synthesized and multi‐morphological complex crew‐cut, star‐like, and short‐chain aggregates were prepared by self‐assembly of the given copolymers. The morphologies and dimensions of the aggregates can be well controlled by variation of the preparation conditions. TEM, SEM, FFR‐TEM, and LLS studies show the resulting morphologies range from LCMs, unilamellar or multilayer vesicles, LCVs, porous spheres to nanorods.

TEM images of the vesicles formed from PEO‐b‐PDMS‐b‐PEO.     

Water‐Developable Poly(2‐oxazoline)‐Based Negative Photoresists

Copoly(2‐oxazoline)‐based photoresists are prepared from pEtOx₈₀Bu⁼Ox₂₀ and pPhOx₈₀Dc⁼Ox₂₀ , respectively, a tetrathiol, and a photosensitive initiator. It is possible to prepare copoly(2‐oxazoline)s bearing unsaturated side chains in a microwave reactor on a decagram scale in reaction times of 100 min or shorter. UV irradiation of dried polymer films through a quartz mask induces the thiol‐ene reaction in the illuminated areas. Subsequent development of the polymer films in halogen‐free solvents reproduces the negative pattern of the mask with a resolution of 2 μm. The pEtOx₈₀Bu⁼Ox₂₀ ‐derived photoresists can also be developed in water.     

Thermoplastic elastomers based on poly(l‐Lysine)‐Poly(ε‐Caprolactone) multi‐block copolymers

Novel thermoplastic elastomers based on multi‐block copolymers of poly(l ‐lysine) (PLL), poly(N‐ε‐carbobenzyloxyl‐l ‐lysine) (PZLL), poly(ε‐caprolactone) (PCL), and poly(ethylene glycol) (PEG) were synthesized by combination of ring‐opening polymerization (ROP) and chain extension via l ‐lysine diisocyanate (LDI). SEC and ¹H NMR were used to characterize the multi‐block copolymers, with number‐average molecular weights between 38,900 and 73,400 g/mol. Multi‐block copolymers were proved to be good thermoplastic elastomers with Young's modulus between 5 and 60 MPa and tensile strain up to 1300%. The PLL‐containing multi‐block copolymers were electrospun into non‐woven mats that exhibited high surface hydrophilicity and wettability. The polypeptide–polyester materials were biocompatible, bio‐based and environment‐friendly for promising wide applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3012–3018     

Response Behavior of Poly(vinyl chloride)‐ and Polyurethane‐Based Ca2+‐Selective Membrane Electrodes with Polypyrrole‐ and Poly(3‐octylthiophene)‐Mediated Internal Solid Contact

The potentiometric response behavior of Ca²⁺‐selective poly(vinyl chloride) (PVC) and polyurethane (PU) membranes with different inner contacts has been compared. Evidence for the formation of a water film between membrane and internal contact and, hence, a less than optimal lower detection limit have been found for membranes directly in contact with bare Au or with polypyrrole generated by electropolymerization in the presence of KCl. A significantly better behavior is shown by membranes with polypyrrole prepared in the presence of potassium hexacyanoferrate. Best performances have been obtained with solvent‐cast poly(3‐octylthiophene) as the internal contacting layer. As compared with the PVC membranes, those with PU had a significantly worse performance throughout.     

Poly(cyclic imino ether)s Beyond 2‐Substituted‐2‐oxazolines

2‐Oxazolines (2‐OZO) are 5‐membered cyclic imino ethers whose cationic ring‐opening polymerization (CROP) mechanism and resulting polymer properties are extensively studied. However, also 6‐ and 7‐membered cyclic imino ethers can be polymerized via CROP. Together with the much less studied 4‐ and 5‐substituted main‐chain chiral poly(2‐oxazoline)s (P‐2‐OZO), these compounds are interesting monomers to enhance the versatility of (co)poly(cyclic imino ether)s. To emphasize the potential of such alternative cyclic imino ether monomers, we provide an overview on the polymerizations of 2‐oxazine (2‐OZI) and chiral 4‐ and 5‐substituted 2‐OZO as well as of selected properties of the resulting polymers. In addition, the hydrolysis of these polymers into the corresponding poly(alkylene imine)s will be addressed.

     

Hierarchical Self‐Assembly of Double‐Crystalline Poly(ferrocenyldimethylsilane)‐block‐poly(2‐iso‐propyl‐2‐oxazoline) (PFDMS‐b‐PiPrOx) Block Copolymers

The step‐wise solution self‐assembly of double crystalline organometallic poly(ferrocenyldimethylsilane)‐block‐poly(2‐iso‐propyl‐2‐oxazoline) (PFDMS‐b‐PiPrOx) diblock copolymers is demonstrated. Two block copolymers are obtained by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), featuring PFDMS/PiPrOx weight fractions of 46/54 (PFDMS₃₀‐b‐PiPrOx₇₅) and 30/70 (PFDMS₃₀‐b‐PiPrOx₁₅₅). Nonsolvent induced crystallization of PFDMS in acetone leads in both cases to cylindrical micelles with a PFDMS core. Afterward, the structures are transferred into water for sequential temperature‐induced crystallization of the PiPrOx corona, leading to hierarchical double crystalline superstructures, which are investigated using scanning electron microscopy, wide angle X‐ray scattering, and differential scanning calorimetry.

     

A Binaphthyl‐Bridged Salen Zirconium Catalyst Affording Atactic Poly(propylene) and Isotactic Poly(α‐olefins)

Summary: A binaphthyl‐bridged salen dichlorozirconium (IV ) complex that displays an octahedral structure with a trans‐O, cis‐N, and cis‐Cl arrangement was synthesized and tested as a precatalyst for ethylene and α‐olefin polymerization. While use of methylaluminoxane (MAO) cocatalyst afforded poor catalytic activity, activation by mixtures of aluminium alkyls such as AlⁱBu₃ and either MAO or [CPh₃][B(C₆F₅)₄] resulted in reasonable polymerization activities for ethylene, propene, and higher α‐olefins. Quite unexpectedly, while the polymerization of propene results in the production of a high‐molecular‐weight stereoirregular polymer, highly isotactic polymers are obtained under similar conditions from polymerization of 1‐butene, 1‐pentene, and 1‐hexene.

Polymerization employing the binaphthyl‐bridged salen dichlorozirconium (IV ) complex gave unexpected different stereospecificities for the polymerization of propene and higher α‐olefins, to yield ultrahigh‐molecular‐weight atactic poly(propylene) and highly isotactic polymers, respectively.