Cleavable multiblock copolymer synthesized by ring‐opening metathesis copolymerization of cyclooctene and macrocyclic olefin and its hydrolysis to give carboxyl‐telechelic polymer

A novel cleavable multiblock copolymer was synthesized by ring‐opening metathesis polymerization (ROMP) of cyclooctene (COE) and a flexible 27‐membered macrocyclic olefin (MCO), which is acted as the spacer to collect the polymer structure block by block. MCO 2 was prepared via ring‐closing metathesis of the long chain alkyldiene, and then 2 was well‐ conducted ROMP with COE to provide the multiblock copolymer [Poly(COE)‐ 2 ]_m consisting of homo‐Poly(COE) blocks and ring‐opened 2 segments with different molecular weights (M_n = 30.0 – 249.6 × 10³) and polydispersity index (PDI) within 1.45–1.67 as variation of the feed ratio of COE to 2 . The multiblock copolymer chain containing weak ester linkage can be cleaved under alkali condition to afford the carboxyl‐telechelic Poly(COE) blocks with much lower molecular weights (M_n,h = 3.6–35.7 × 10³) and slight higher PDIs (1.65–1.88). The average block number on multiblock copolymer chain was obtained from the ratio of M_n to M_n,h and was reached up to the value of 7–16. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 380–388, 2010     

Easy Access to Diverse Multiblock Copolymers with On-Demand Blocks via Thioester-Relayed In-Chain Cascade Copolymerization

Multiblock copolymers are envisioned as promising materials with enhanced properties and functionality compared with their diblock/triblock counterparts. However, the current approaches can construct multiblock copolymers with a limited number of blocks but tedious procedures. Here, we report a thioester-relayed in-chain cascade copolymerization strategy for the easy preparation of multiblock copolymers with on-demand blocks, in which thioester groups with on-demand numbers are built in the polymer backbone by controlled/living polymerizations. These thioester groups further serve as the in-chain initiating centers to trigger the acyl group transfer ring-opening polymerization of episulfides independently and concurrently to extend the polymer backbone into multiblock structures. The compositions, number of blocks, and block degree of polymerization can be easily regulated. This strategy can offer easy access to a library of multiblock copolymers with ≈100 blocks in only 2 to 4 steps.     

A chain geometry prediction of polystyrene and polyarylate block copolymer by a kinetic simulation model

The chain geometry of polystyrene (PS) and polyarylate (PAr) block copolymer was predicted by the simulation of the kinetics of the block‐copolymerization route. The simulation model consisted of a combination of two models. In the first model, the kinetics of the free‐radical polymerization of carboxyl‐terminated telechelic PS (COOH‐PS‐COOH) was simulated for the determination of the molecular weight distribution. In the second model, the kinetics of the PS and PAr block copolymerization with COOH‐PS‐COOH was simulated by a Monte Carlo computation, with each reacting functional group assigned by an integer. The number‐average and weight‐average molecular weights and the composition of the PS‐PAr block copolymer, as calculated by the simulation models, were in good agreement with the experimental data. From this agreement, plausible predictions for the chain geometry (i.e., the type of block copolymer and length of each segment) were obtained that were practically impossible to analyze experimentally. The simulation results showed that more than 80 wt % of the block copolymer synthesized by this method was a composite of various types of multiblock copolymers and that the length of the PAr segment was almost the same as that of the homo‐PAr obtained as a by‐product. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 299–309, 2000     

Window consensus PCA for multiblock statistical process control: adaption to small and time‐dependent normal operating condition regions,illustrated by online high performance liquid chromatography of a three‐stage continuous process

A method for multiblock statistical process control is described, involving the computation of Q and D statistics both for individual blocks and for the overall process using window consensus principal components analysis (WCPCA). The approach overcomes two common problems. The first is a small normal operating conditions (NOC) region, which is done by determining the Q‐statistic limits and D statistics using leave‐one‐out (LOO) residuals and scores, rather than employing the residuals and scores of a single training set model obtained from the entire NOC region. The second overcomes the problem of temporal drift of the process and/or measurement technique by updating the NOC covariance matrix to adapt to normal process changes. The unifying multiblock statistical process control and relevant statistics are adapted to cope with these issues and are illustrated in this paper using CPCA as applied to online high performance liquid chromatography (HPLC) of a three‐stage continuous process. Copyright © 2010 John Wiley & Sons, Ltd.     

聚对苯二甲酸丁二酯-聚四亚甲基醚多嵌段共聚物的研究

合成了硬段含量和软段分子量不同的聚对苯二甲酸丁二酯-聚四亚甲基醚(PBT-PTMG)多嵌段共聚物。研究了硬段含量和软段分子量对嵌段共聚合过程的影响。当软段分子量较大、硬段含量较高时,在嵌段共缩聚过程中有均聚物伴生。当软段分子量在2000左右,硬段含量在20％左右时,基本上不生成均聚物。硬段重量含量为 20％的低硬段 PBT-PTMG多嵌段共聚物是结晶的。由它纺成的弹体纤维有良好的力学性能和弹性回复。热处理能改进纤维的弹性回复。     

Multiblock variance partitioning: a new approach for comparing variation in multiple data blocks

More than one multi-informative analytical technique is often applied when describing the condition of a set of samples. Often a part of the information found in these data blocks is redundant and can be extracted from more blocks. This study puts forward a method (multiblock variance partitioning—MVP) to compare the information/variation in different data blocks using simple quantitative measures. These measures are the unique part of the variation only found in one data block and the common part that can be found in more data blocks. These different parts are found using PLS models between predictor blocks and a common response. MVP provides a different view on the information in different blocks than normal multiblock analysis. It will be shown that this has many applications in very diverse fields such as process control, assessor performance in sensory analysis, efficiency of preprocessing methods and as complementary information to an interval PLS analysis. Here the ideas of the MVP approach are presented in detail using a study of red wines from different regions measured with GC-MS and FT-IR instruments providing different kinds of data representations.     

A study for the static properties of symmetric linear multiblock copolymers under poor solvent conditions

We use a standard bead-spring model and molecular dynamics simulations to study the static properties of symmetric linear multiblock copolymer chains and their blocks under poor solvent conditions in a dilute solution from the regime close to theta conditions, where the chains adopt a coil-like formation, to the poorer solvent regime where the chains collapse obtaining a globular formation and phase separation between the blocks occurs. We choose interaction parameters as is done for a standard model, i.e., the Lennard-Jones fluid and we consider symmetric chains, i.e., the multiblock copolymer consists of an even number n of alternating chemically different A and B blocks of the same length N(A) = N(B) = N. We show how usual static properties of the individual blocks and the whole multiblock chain can reflect the phase behavior of such macromolecules. Also, how parameters, such as the number of blocks n can affect properties of the individual blocks, when chains are in a poor solvent for a certain range of n. A detailed discussion of the static properties of these symmetric multiblock copolymers is also given. Our results in combination with recent simulation results on the behavior of multiblock copolymer chains provide a complete picture for the behavior of these macromolecules under poor solvent conditions, at least for this most symmetrical case. Due to the standard choice of our parameters, our system can be used as a benchmark for related models, which aim at capturing the basic aspects of the behavior of various biological systems.     

High-order multiblock copolymers via iterative Cu(0)-mediated radical polymerizations (SET-LRP): toward biological precision

We report a new approach for the facile synthesis of high-order multiblock copolymers comprising very short blocks. The approach entails sequential addition of different monomers via an iterative single electron transfer-living radical polymerization technique, allowing nearly perfect control of the copolymer microstructure. It is possible to synthesize high-order multiblock copolymers with unprecedented control, i.e., A-B-C-D-E-etc., without any need for purification between iterative 24 h block formation steps. To illustrate this concept, we report the synthesis of model P(MA-b-MA...) homopolymer and P(MA-b-nBuA-b-EA-b-2EHA-b-EA-b-nBuA) copolymer in extremely high yield. Finally, the halide end-group can be modified via "click chemistry", including thiol-bromide click chemistry, sodium methanethiosulfonate nucleophilic substitution, and atom transfer radical nitroxide coupling reaction, to yield functional, structurally complex macromolecules.     

Integral equation theory of randomly coupled multiblock copolymer melts: effect of block size on the phase behavior

The phase behavior of randomly coupled multiblock copolymer melts is studied using the polymer reference interaction site model integral equation theory. The molecules are modeled as flexible chains with random sequences of two types of blocks, each of which consists of the same number (R) of monomer beads. In the random copolymer (R=1) limit the theory predicts macrophase separation as the temperature is decreased for all values of the monomer correlation length lambda. For R>2, however, the theory predicts a microphase separation for values of lambda less than some critical value which increases as the block size increases.     

Thermo-induced formation of unimolecular and multimolecular micelles from novel double hydrophilic multiblock copolymers of N,N-dimethylacrylamide and N-isopropylacrylamide

Two novel double hydrophilic multiblock copolymers of N,N-dimethylacrylamide and N-isopropylacrylamide, m-PDMAp-PNIPAMq, with varying degrees of polymerization (DPs) for PDMA and PNIPAM sequences (p and q) were synthesized via consecutive reversible addition-fragmentation chain transfer (RAFT) polymerizations using polytrithiocarbonate (1) as the chain transfer agent (Scheme 1), where PDMA is poly(N,N-dimethylacrylamide) and PNIPAM is poly(N-isopropylacrylamide). The DPs of PDMA and PNIPAM sequences were determined by 1H NMR, and the block numbers, i.e., number of PDMAp-PNIPAMq sequences (n), were obtained by comparing the molecular weights of multiblock copolymers to that of cleaved products as determined by gel permeation chromatography (GPC). m-PDMA42-PNIPAM37 and m-PDMA105-PNIPAM106 multiblock copolymers possess number-average molecular weights (Mn) of 4.62x10(4) and 9.53x10(4), respectively, and the polydispersities (Mw/Mn) are typically around 1.5. Block numbers of the obtained multiblock copolymers are ca. 4, which are considerably lower than the numbers of trithiocarbonate moieties per chain of 1 (approximately 20) and m-PDMAp precursors (approximately 6-7). PDMA homopolymer is water soluble to 100 degrees C, while PNIPAM has been well known to exhibit a lower critical solution temperature (LCST) at ca. 32 degrees C. In aqueous solution, m-PDMA42-PNIPAM37 and m-PDMA105-PNIPAM106 multiblock copolymers molecularly dissolve at room temperature, and their thermo-induced collapse and aggregation properties were characterized in detail by a combination of optical transmittance, fluorescence probe measurements, laser light scattering (LLS), and micro-differential scanning calorimetry (micro-DSC). It was found that chain lengths of PDMA and PNIPAM sequences exert dramatic effects on their aggregation behavior. m-PDMA105-PNIPAM106 multiblock copolymer behaves as protein-like polymers and exhibits intramolecular collapse upon heating, forming unimolecular flower-like micelles above the thermal phase transition temperature. On the other hand, m-PDMA42-PNIPAM37 multiblock copolymer exhibits collapse and intermolecular aggregation, forming associated multimolecular micelles at elevated temperatures. The intriguing aggregation behavior of this novel type of double hydrophilic multiblock copolymers argues well for their potential applications in many fields such as biomaterials and biomedicines.     

Iterative weighting of multiblock data in the orthogonal partial least squares framework

The integration of multiple data sources has emerged as a pivotal aspect to assess complex systems comprehensively. This new paradigm requires the ability to separate common and redundant from specific and complementary information during the joint analysis of several data blocks. However, inherent problems encountered when analysing single tables are amplified with the generation of multiblock datasets. Finding the relationships between data layers of increasing complexity constitutes therefore a challenging task. In the present work, an algorithm is proposed for the supervised analysis of multiblock data structures. It associates the advantages of interpretability from the orthogonal partial least squares (OPLS) framework and the ability of common component and specific weights analysis (CCSWA) to weight each data table individually in order to grasp its specificities and handle efficiently the different sources of Y-orthogonal variation.     

Synthesis and properties of sulfonated multiblock copoly(ether sulfone)s by a chain extender

A new series of sulfonated multiblock copoly(ether sulfone)s applicable to proton exchange membrane fuel cells was synthesized. The multiblock copolymers were synthesized by the nucleophilic aromatic substitution of hydroxyl‐terminated oligomers in the presence of highly reactive decafluorobiphenyl (DFB) as a chain extender. Because of the high reactivity of DFB, the ether–ether interchange reaction, which could lead to a randomized polymer architecture, was prevented, and multiblock copolymers with high molecular weights were easily produced. The multiblock copolymers gave tough, flexible, and transparent membranes by solution casting. The ion exchange capacity values could be easily controlled by changing the sulfonated block ratios in the copolymers. The resulting membranes demonstrated good oxidative and dimensional stability and significantly higher proton conductivity than sulfonated random poly(ether sulfone) copolymers. The morphologies of the membranes were investigated by tapping mode atomic force microscopy, which showed that the multiblock membranes had a clear hydrophilic/hydrophobic separated structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3947–3957, 2008     

Multiblock copolymers of poly(2,5‐benzophenone) and disulfonated poly(arylene ether sulfone) for proton‐exchange membranes. I. Synthesis and characterization

Nanophase‐separated, hydrophilic–hydrophobic multiblock copolymers are promising proton‐exchange‐membrane materials because of their ability to form various morphological structures that enhance transport. A series of poly(2,5‐benzophenone)‐activated, telechelic aryl fluoride oligomers with different block molecular weights were successfully synthesized by the Ni(0)‐catalyzed coupling of 2,5‐dichlorobenzophenone and the end‐capping agent 4‐chloro‐4′‐fluorobenzophenone. These telechelic oligomers (hydrophobic) were then copolymerized with phenoxide‐terminated, disulfonated poly(arylene ether sulfone)s (hydrophilic) by nucleophilic, aromatic substitution to form hydrophilic–hydrophobic multiblock copolymers. High‐molecular‐weight multiblock copolymers with number‐average block lengths ranging from 3000 to 10,000 g/mol were successfully synthesized. Two separate glass‐transition temperatures were observed via differential scanning calorimetry in the transparent multiblock copolymer films when each block length was longer than 6000 g/mol. Tapping‐mode atomic force microscopy also showed clear nanophase separation between the hydrophilic and hydrophobic domains and the influence of the block length as it increased from 6000 to 10,000 g/mol. Transparent and creasable films were solvent‐cast and exhibited moderate proton conductivity and low water uptake. These copolymers are promising candidates for high‐temperature proton‐exchange membranes in fuel cells, which will be reported separately in part II of this series. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 284–294, 2007     

Multiblock copolymers of styrene and isoprene. I. Synthesis and characterization

An anionic polymerization procedure for preparing multiblock copolymers of styrene and isoprene is described. The process is based on the initial specific incorporation of isoprene when mixtures of styrene and isoprene are polymerized with butyllithium in hydrocarbon solution. As examples, linear (AB)₃ block copolymers have been prepared by interrupting styrene polymerization by step additions of isoprene at times programmed according to the reactivity ratios and the rate constants for styrene and isoprene propagations. The products were characterized by means of osmometry, light scattering, gel-permeation chromatography, and density-gradient ultracentrifugation. The analyses showed that the multiblock copolymers are free from polymeric impurities and reasonably homogeneous in molecular weight and composition. The polystyrene segment lengths were analyzed by means of GPC after the oxidative degradation of the polyisoprene moieties in the copolymers. The results suggest that the polyisoprene blocks contain a nonnegligible amount of styrene but that this monomer is incorporated as very short segments. On the other hand the polystyrene blocks produced at the end of the copolymerizations appear to have narrow molecular weight distributions.     

A styryl tipno‐based nitroxide as efficient mediator for the synthesis of multiblock polystyrenes and well‐grafted polymers

The chloromagnesium exchange of 4‐chlorostyrene provides an easy access to a new versatile polymerizable 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐nitroxide (TIPNO)‐based nitroxide. Indeed, first, its alkoxyamine based on the α‐methyl benzyl radical fragment efficiently mediates the polymerization of styrene (respectively n‐butyl acrylate) to yield branched polystyrene [respectively poly(n‐butyl acrylate)] with alkoxyamine function as branch point and well‐defined branches. Second, the self‐condensing of this polymerizable nitroxide by manganese coupling affords a mixture of oligomeric linear polyalkoxyamines. Polymerization of styrene mediated with these polyalkoxyamines gives multiblock polystyrenes with alkoxyamine group as linker between polystyrene blocks and exhibits the following features: the synthesis of the polystyrene blocks is controlled as their average molecular weight M_n(block) increases linearly with conversion and their average dispersity M_w/M_n(block) decreases with it. At a given temperature, the molecular weight and the dispersity of the polyalkoxyamines weakly impact M_n(block) and M_w/M_n(block). In contrast, the molecular weight of the multiblock polystyrene increases linearly with conversion until reaching a constant value. The number of block is independent of the molecular weight of the polyalkoxyamines. These unusual results can be explained by the fact that during polymerization, mediating TIPNO‐based polymeric nitroxides with different lengths are generated and are exchanged. Finally the dispersity of the multiblock polystyrene is quite broad and lies between 1.7 and 2.8. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Ambient temperature ATRP of benzyl methacrylate as a tool for the synthesis of block copolymers with styrene

The rapid atom transfer radical polymerization (ATRP) of benzyl methacrylate (BnMA) at ambient temperature was used to synthesize block copolymers with styrene as the second monomer. Various block copolymers such as AB diblock, BAB symmetric and asymmetric triblock, and ABABA pentablock copolymers were synthesized in which the polymerization of one of the blocks namely BnMA was performed at ambient temperature. It is demonstrated that the block copolymerization can be performed in a controlled manner, regardless of the sequence of monomer addition via halogen exchange technique. Using this reaction condition, the composition (ratio) of one block (here BnMA) can be varied from 1 to 100. It is further demonstrated that in the multiblock copolymer syntheses involving styrene and benzyl methacrylate, it is better to start from the PS macroinitiator compared with PBnMA macroinitiator. The polymers synthesized are relatively narrow dispersed (<1.5). It is identified that the ATRP of BnMA is limited to certain molecular weights of the PS macroinitiator. Additionally, a preliminary report about the synthesis of the block copolymer of BnMA‐methyl methacrylate (MMA), both at ambient temperature, is demonstrated. Subsequent deprotection of the benzyl group using Pd/C? H₂ results in methacrylic acid (MAA)–methyl methacrylate (MAA–MMA) amphiphilic block copolymer. GPC, IR, and NMR are used to characterize the synthesized polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2848–2861, 2006     

Ionomers for proton exchange membrane fuel cells by sulfonation of novel dendritic multiblock copoly(ether‐sulfone)s

The synthesis and properties of the first examples of dendritic multiblock co PES s, bearing sulfonated dendritic clusters, that form strong membranes are described. End‐capped dendritic multiblock co PES s with various average block lengths (n = 50–80) were synthesized by two‐step reactions. The synthesis of dendritic blocks consisting of difunctional dendritic block and monofunctional dendritic end‐group was accomplished by an aromatic nucleophilic substitution reaction of hexakis(4‐(4‐fluorophenylsulfonyl)phenyl)benzene with varying amounts of 1‐(4‐hydroxyphenyl)‐2,3,4,5,6‐pentaphenylbenzene, which provides a number of pendant phenyl rings as postsulfonation sites. Polycondensation of a controlled molar ratio between 4,4′‐dihydroxybenzophenone and bis(4‐fluorophenyl)sulfone monomers was carried out in the presence of the difunctional and monofunctional dendritic blocks in sulfolane at 215 °C for 3.5 h. Essentially six sulfonic acid groups were introduced into each hexaphenylbenzene moiety on the dendritic blocks by reaction with a large excess of chlorosulfonic acid, followed by hydrolysis with KOH aqueous solution. The introduction of longer average blocks (n = 60–80) into the dendritic PES s improved the mechanical properties of the resulting sulfonated dendritic PES membranes. At a level of IEC (0.92–1.26 meq/g) similar to Nafion (0.91 meq/g), PES membranes showed proton conductivities (58–67 mS/cm) comparable with that of Nafion (99 mS/cm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5461–5473, 2009     

Multiblock poly(4‐vinylpyridine) and its copolymer prepared with cyclic trithiocarbonate as a reversible addition–fragmentation transfer agent

The polymerization of 4‐vinylpyridine was conducted in the presence of a cyclic trithiocarbonate (4,7‐diphenyl‐[1,3]dithiepane‐2‐thione) as a reversible addition–fragmentation transfer (RAFT) polymerization agent, and a multiblock polymer with narrow‐polydispersity blocks was prepared. Two kinds of multiblock copolymers of styrene and 4‐vinylpyridine, that is, (ABA)_n multi‐triblock copolymers with polystyrene or poly(4‐vinylpyridine) as the outer blocks, were prepared with multiblock polystyrene or poly(4‐vinylpyridine) as a macro‐RAFT agent, respectively. GPC data for the original polymers and polymers cleaved by amine demonstrated the successful synthesis of amphiphilic multiblock copolymers of styrene and 4‐vinylpyridine via two‐step polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2617–2623, 2007     

Phase behavior and Li+ Ion conductivity of styrene‐ethylene oxide multiblock copolymer electrolytes

Solid polymer electrolytes are attractive materials for use as battery separators. Here, a molecular weight series of polystyrene–polyethylene oxide (PEO) multiblock copolymers was synthesized by the thiol–norbornene click reaction. The subsequent materials were characterized both neat and with a lithium bis‐(trifluoromethane)sulfonimide salt loading [(Li)/(EO)] of 0.1. In general, neat samples demonstrated crystallinity scaling with PEO content. Lithium ion‐containing samples had broad scattering peaks, half of which displayed disordered scattering, even at the lowest block molecular weights (polystyrene = 1 kg/mol, PEO = 1 kg/mol). Fitting of disordered scattering data, using the random phase approximation, yielded χ_RPA and R_g values that were compared with recent predictive work by Balsara and coworkers. The predictions were accurate near the volume fraction f_PEO = 0.5 but deviated symmetrically with volume fraction asymmetry. Samples were also analyzed by electrochemical impedance spectroscopy for their potential to conduct lithium ions. Samples with f_PEO ≥ 0.5 demonstrated robust conductivity, whereas samples below this volume fraction conducted very poorly, with one exception (f_PEO = 0.24). This work expanded upon our recently reported approach to multiblock copolymer synthesis, demonstrating the improved access of materials to further our fundamental understanding of multiblock copolymers. Copyright © 2016 John Wiley & Sons, Ltd.     

Sulfonated multiblock copoly(ether sulfone)s as membrane materials for fuel cell applications

Arylene ether multiblock copolymers of the (AB)_n-type with various degrees of sulfonation have been prepared by a two-step polycondensation procedure. Multiblock copolymers in high yields and of high molecular weights were obtained. For comparison random copolymers with the same overall composition were synthesized. The theoretical ion-exchange capacities (IEC) of the materials were ranging from 0.50 mmol/g to 1.25 mmol/g. The water-uptake of the multiblock copolymers showed a linear dependency from the IEC and was increasing with increasing IEC. No differences were observed between random and block copolymers. Furthermore, the hydrolytic stability of aromatic sulfonic acid groups was investigated in this study. Aromatic sulfonic acids, having additional electron donating groups, especially in ortho- or para-position to the sulfonic acid group are sensitive to hydrolytic desulfonation. On the other hand electron-withdrawing groups in meta-position showed a stabilizing effect.