Journal of Polymer Science Part A: Polymer Chemistry

On page 1533, Adam B. Braunschweig and colleagues investigate the suitability of different polymer compositions of tip arrays for polymer pen lithography (PPL), and the mandala of tip arrays represents the nearly limitless number of polymer combinations that could be suitable for PPL printing. In the center is an optical microscopy image of a pen array, with the chemical structures of different polymers (polydimethylsiloxane, poly(methyl methacrylate), poly([methyl methacrylate]-co-[butyl methacrylate]), and poly(3-mercaptopropylmethylsiloxane)) that were explored to generate the pen arrays. In the corners of the mandala are scanning electron micrographs of pyramidal tips within these arrays. The mandala is superimposed on images and graphs that represent the time- and force-dependent printing that are the hallmarks of this powerful nanolithography technique.

Research in polymer science and engineering is moving from classical methodologies to advanced analytical strategies in which mass spectrometry (MS)-based techniques play a crucial role. The molecular complexity of polymers requires new characterization tools and approaches to elucidate the detailed structural information. In the work by Ulrich S. Schubert and colleagues on page 1595, a comparison study using different tandem MS techniques (ESI, APCI, and MALDI MS/MS) is reported to provide insights into the macromolecular structure of polymers with the aid of a special MS/MS data interpretation software. The application of a tailor-made software is shown to analyze complex MS/MS data, and it is shown that this kind of software will be helpful for polymer scientists to identify fragmentation products obtained by tandem MS, for instance in the fields of proteomics, metabolomics, genomics, and glycomics.

Soft ionization mass spectroscopy is a powerful technique for characterizing polymer structures. A brief description of the different spectrometric techniques available for polymer analyses, including MALDI-TOF, ESI-MS, and other recent methods, is given. The techniques are compared and the limitations and advantages are discussed. The possible side reactions that can occur during MALDI-TOF analysis are detailed and the importance of correct sample preparation is emphasized. ESI-MS is also given attention and emphasis is placed on the limitations and optimization of samples for successful analyses.

A low band gap alternative polymer was synthesized. The polymer contained benzodithiophenes with lateral thiophenes and fluorinated benzothiadiazole. The polymer possessed broad absorption and high V_oc. The PCE of the device with PC₆₁BM achieved 4.8% without annealing and additive.

A series of polyfluorene-based copolymers with pyrene units have been synthesized and characterized for use in polymer solar cells. Under optimized conditions, the polymers display PCEs for the PSCs in the range 1.99–3.37% under AM 1.5 illumination (100 mW cm⁻²). The PCEs of polymer solar cells are improved from 2.11% for devices prepared without pyrene to 3.37% for devices prepared with pyrene.

In this contribution, the synthesis of a β-triketimine ligand ({2,4,6-CH₃C₆H₂NC(CH₃)}₃CH) and its Ni complex has been reported as a catalyst precursor for ethylene polymerization. Response surface method (RSM) has been applied successfully for investigation of operational conditions; it provides predictive models for activity, weight-average molecular weight (M_w), and crystallinity with adequate goodness-of-fit. It also provides operational conditions for reaching user-defined values of activity, M_w, and crystallinity. The resultant activities challenge the best achieved with nickel bearing β-diimine-derived ligands.

Tip-arrays for polymer pen lithography (PPL) were prepared from poly(dimethyl siloxane), poly(methyl methacrylate), poly([methyl methacrylate]-co-[butyl methacrylate]), and poly(3-mercaptopropylmethylsiloxane) to explore the role of polymer mechanical properties on the force-dependent ink transfer. Ink was transferred successfully for all materials except poly([methyl methacrylate]-co-[butyl methacrylate]), and it was foundthat the relationship between force and feature edge length is governed by the mechanical properties of the polymers that comprise the tip-arrays.

A new titanium complex bearing an asymmetric ligand has been synthesized and characterized. This complex has been found to catalyze aqueous homopolymerization and copolymerization of MMA and styrene at room temperature to afford polymer nanoparticles. The polymers obtained are of very high molecular weights.

Electron-transporting or ambipolar solution-processable polymers consisting of perylene diimide (PDI) acceptor moieties alternating with dithienothiophene (DTT), N-dodecyl-dithienopyrrole (DTP), or oligomers of these donor groups have been synthesized. In addition to varying the donor, the N,N′ substiuents of the PDIs have also been varied. The thermal, optical, electrochemical, and charge-transport properties of the polymers have been investigated. There is considerable variation in the charge transport properties of the polymers with the chemical structures.

Single electron transfer living radical polymerization of methyl methacrylate catalyzed by the in situ prepared Cu(0) at ambient temperature was first examined using various metallic powders, including Zn(0), Ni(0), Mg(0), and Fe(0). The polymerization initiated with the Ni(0)/EBiB/CuBr₂/PMDETA system exhibited optimal living/controlled nature and generated polymers with PDI as low as 1.04 for 75.27% conversion and controlled molecular weights close to theoretical values. A wide of range of Cu(II) salts were also investigated as catalyst sources instead of CuBr₂. The recycling of Ni(0) was very convenient due to its magnetic property, which enables its extensive application.

Four D-A polymers with the same main chain based on benzodithiophene and quinoxaline but with differently conjugated donor groups at the acceptor units are synthesized to investigate the impact of the conjugated side chains at the acceptor units on the photovoltaic properties of D-A polymers. The performance of the solar cells increases when thienyl or phenylene thienyl groups are used, but decreases when additional thienyl groups are added at the side chains.

The dispersion RAFT polymerization of 4-vinylpyridine in toluene in the presence of the polystyrene dithiobenzoate (PS-CTA) macro-RAFT agent with different chain lengths is discussed. It is found that that the PS-CTA chain length exerts a great influence on the polymerization kinetics, the particle nucleation and the particle morphology of the synthesized block copolymers. That is, short PS-CTA generally leads to fast RAFT polymerization and fast particle nucleation, and tends to produce large-sized vesicles or large-compound micelles.

A series of o-di(phenyl)phosphanylphenolate-based half-titanocene complexes CpTiCl₂[O-2-R¹-4-R²-6-(Ph₂P)C₆H₂] have been synthesized. Surprisingly, notable improvements in the catalytic activity were observed if introducing norbornene (NBE) into the system, and catalytic activity was more than 100 times larger than that of ethylene homopolymerization in the case of Ph₃CB(C₆F₅)₄/ⁱBu₃Al as cocatalyst. By carrying out DFT calculations, the active species is predicted and the role of NBE is identified.

A comparison study of poly(methyl acrylate)s (PMA) using different (tandem) mass spectrometry techniques (ESI, APCI, MALDI MS, and MS/MS) is reported to provide insights into the macromolecular structure. Collision-induced dissociation (CID) experiments are performed to examine the fragmentation pathways of PMAs synthesized via various controlled radical polymerization (CRP) techniques. Fragmentation products are identified with the help of a dedicated tandem MS data interpretation software.

This article describes the studies on the catalytic activity of several nitrogen-based organic catalysts for the depolymerization of poly(ethylene terephthalate) (PET), in which a few cyclic amidines work more effectively than a potent, bifunctional guanidine-based catalyst 1,5,7-triazabicyclo-[4,4,0]-dec-5-ene (TBD) in the presence of short-chain diols that play a role in activation of carbonyl groups through hydrogen bonding. Further studies show that the catalytic efficiency at the above specific conditions depends only on the extent of activation of a hydroxyl group rather than simply the pK_a of the bases. For glycolysis with excess short-chain alkanediols, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is the best catalyst. In contrast, TBD shows outstanding catalytic activity in depolymerizations of PET with mono-alcohols and longer-chain diols.

In this study, highly pH-responsive mixed-charged copolymer brushes are reported containing negatively charged carboxylic acid monomers (4-vinylbenzoic acid) and positively charged quaternary amine monomers ((ar-vinylbenzyl)trimethylammonium chloride) via reversible addition–fragmentation chain transfer-mediated polymerization. The brushes have negative charge under neutral and basic conditions, and are positively charged under acidic conditions owing to the protonation of the carboxylic acid groups.

New hydroxyl-terminated amphiphilic block copolymer micellar aggregates having pendant t-butyl groups for pH-responsiveness and terminal OH groups for bioconjugation synthesized by a consecutive atom transfer radical polymerization in the presence of an OH-terminated bromine initiator.

The use of a phenol-modified methylaluminoxane (MAO) cocatalyst for the synthesis of ultrahigh molecular weight polyethylene with a reduced number of entanglements is presented. The research aims, with the help of rheological analyses, to study the effects that a cocatalyst modifier has on the catalytic system performance and on the polymer produced. The results suggest that on using the phenol-modified MAO as cocatalyst, a higher number of active sites are obtained.

A coil-rod-coil copolymer (PEG-OEPETPT-PEG) has been synthesized in one-step via Sonogashira coupling polymerization using two bifunctional small molecular mononers to form the conjugated block and one monofunctional macromolecular monomer as the coil block. The introduction of the coil onto the conjugated block retards the aggregation induced by water and therefore enhances the emission and improves the fluorescence stability of PEG-OEPETPT-PEG compared to the conjugated polymer counterpart without the coils.

In one pot, two-click reactions take place sequentially by adding the reactants step by step. The first click reaction is to produce the monomer for the second click polymerization. The click polymerization differs from the general click polymerization with the reaction of diazide and dialkyne. Nitrile oxides, produced in situ by the first click reaction, are used instead of azides, avoiding the poisonousness and explosiveness. The 3,5-disubstitute polyisoxazoles are produced by the copper(I) catalyzed 1,3-dipolar cycloaddition of nitrile oxides and alkynes with M_w/M_n < 1.2.

The effect of polymerization conditions on anionic ring-opening polymerization behaviors of the five-membered cyclic carbonate, MBCG, is investigated. The corresponding polymers are obtained in high yield by using stronger nucleophilic initiators such as n-butyllithium, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

A cyclic selenium-based RAFT agent, RAFT-Se, was utilized in the RAFT polymerizations of VAc. RAFT-Se showed better control over molecular weights than its analog, RAFT-S. One or more RAFT-Se was incorporated into the resultant poly(VAc) main chain due to the cyclic structure. Considering the biofunction of PVAc-related polymer and the Se-containing material, this work undoubtedly presents a good junction of both.

A modular synthesis approach with living anionic polymerization is presented for the preparation of well-defined graft (co)polymers. Hydrozirconation of 1,2-polybutadiene and halogenolysis is achieved for controlled synthesis of the reactive backbone, which was coupled with living polymers for well-defined graft polymers. Both the backbone and the side chain are nicely designed by living anionic polymerization, for series graft polymers with tunable size, chemical composition, and grafting density.

Host-guest complexation of 9-dicyanomethylenefluorene (an electron-accepting molecule) into γCD cavities leads to the improvement of the fluorescence efficiency by protection from solvent quenching (decreasing nonradiative decay pathways), and hinders the aggregation tendency with beneficial effects on morphological and adhesion properties.