Polystyrene Macroinitiator Research Articles

Influence of hydrophilic block length on the aggregation properties of polyglycidol-polystyrene-polyglycidol copolymers.

Amphiphilic triblock copolymers, polyglycidol-polystyrene-polyglycidol (PGL-PS-PGL), were synthesised via anionic polymerization starting from the synthesis of a polystyrene macroinitiator with 60 styrene units in the block terminated by ethylene oxide. Poly(ethoxyethyl glycidyl ether) blocks of different lengths were created on both sides of the macroinitiator. By removing the ethoxyethyl blocking groups, PGL-PS-PGL copolymers containing polyglycidol blocks with DP 11, 23, 44 and 63 were received. Their structures were determined by NMR and FTIR. The hydrophilicity of PLG-PS-PGL films was studied upon exposure to water vapour. To perform the copolymers' aggregation in water, the samples were dialysed from DMF into water. The critical concentration of their micellisation (CMC) was determined by measuring the absorbance of the 1,6-diphenylhexa-1,3,5-triene (DPH) probe and the intensity of light scattered by the copolymers' solution as a function of concentration. CMC values increased with increasing the number of hydrophilic glycidol units in the copolymer chain. The sizes of aggregates formed slightly above the critical concentration were measured by dynamic light scattering (DLS), and particles were imaged by cryo-TEM. Cryo-TEM pictures showed the presence of regular micelles in copolymer dispersions. For copolymers with shorter PGL chains aggregated partices were detected. Moreover, cryo-TEM demonstrated that the copolymers with a polyglycidol block of DP = 63 formed regular spherical micelles that formed 2D ordered organisation on the surface. X-ray measurements showed the formation of a partially crystallised PS core in the micelle's interior. The aggregates of all copolymers were stable. Their sizes did not change after one year of storage. The particles did not disassociate even after diluting their dispersions to a concentration 10 times lower than the critical concentration.

Polystyrene-b-Poly(2-(Methoxyethoxy)ethyl Methacrylate) Polymerization by Different Controlled Polymerization Mechanisms.

Functional polymers have been an important field of research in recent years. With the development of the controlled polymerization methods, block-copolymers of defined structures and properties could be obtained. In this paper, the possibility of the synthesis of the functional block-copolymer polystyrene-b-poly(2-(methoxyethoxy)ethyl methacrylate) was tested. The target was to prepare the polymer of the number average molecular weight (Mn) of approximately 120 that would contain 20–40% of poly(2-(methoxyethoxy)ethyl methacrylate) by mass and in which the polymer phases would be separated. The polymerization reactions were performed by three different mechanisms for the controlled polymerization—sequential anionic polymerization, atomic transfer radical polymerization and the combination of those two methods. In sequential anionic polymerization and in atomic transfer radical polymerization block-copolymers of the desired composition were obtained but with the Mn significantly lower than desired (up to 30). The polymerization of the block-copolymers of the higher Mn was unsuccessful, and the possible mechanisms for the unwanted side reactions are discussed. It is also concluded that combination of sequential anionic polymerization and atomic transfer radical polymerization is not suitable for this system as polystyrene macroinitiator cannot initiate the polymerization of poly(2-(methoxyethoxy)ethyl methacrylate).

Synthesis of poly (n-butyl acrylate) with tempo by nitroxide mediated polymerization method

It has been observed that acrylate monomers are very difficult to polymerize with the low cost nitroxide catalyst 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO). Therefore, costly acyclic nitroxides such as N-tert-butyl-N-(1-diethylphosphono-2,2-dimethyl)-N-oxyl, (SG1), 2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) and TIPNO derivatives have to be used for the polymerization of the acrylic acid derivatives. There are very few reports on the use of TEMPO-derivatives toward the polymerization of n-butyl acrylate. Generally different reducing agents viz. glucose, ascorbic acid, hydroxyacetone etc. have been used to destroy excess TEMPO during the polymerization reaction. The acrylate polymerizations fail in the presence of TEMPO due to the strong C–O bond formed between the acrylate chain end and nitroxide. To the best of our knowledge, no literature report is available on the use of TEMPO without reducing agent or high temperature initiators, toward the polymerization of n-butyl acrylate. The present study has been carried out with a view to re-examine the application of low cost nitroxide TEMPO, so that it can be utilized towards the polymerization of acrylate monomers (e.g. n-butyl acrylate). We have been able to polymerize n-butyl acrylate using the nitroxide TEMPO as initiator (via a macroinitiator). In this synthesis, a polystyrene macroinitiator was synthesized in the first step from TEMPO, after this TEMPO end-capped styrene macroinitiator (PSt-TEMPO) is used to polymerize n-butyl acrylate monomer. The amount of macroinitiator taken was varied from 0.05% to 50% by weight of n-butyl acrylate monomer. The polymerization was carried out at 120°C by bulk polymerization method. The experimental findings showed a gradual increase in molecular weight of the polymer formed and decrease in the polydispersity index (PDI) with increase in amount of PSt-TEMPO macroinitiator taken. In all experiments conversion was more than 80%. These results indicate that the polymerization takes place through controlled polymerization process. Effect of different solvents on polymerization has also been investigated. In the following experiments TEMPO capped styrene has been used as macroinitiator leading to the successful synthesis of poly n-Butyl acrylate. It has been found that styrene macroinitiator is highly efficient for the nitroxide mediated polymerization, even in very small concentration for the synthesis of poly n-butyl acrylate. High concentration of macroinitiator results in the formation of block copolymers of polystyrene and poly ( n-butyl acrylate) viz. polystyrene-block-poly-( n-butyl acrylate). The use of TEMPO toward controlled polymerization is of much importance, because it is the nitroxide commercially available at the lowest cost.

Temperature Variation Enables the Design of Biobased Block Copolymers via One-Step Anionic Copolymerization.

A one-pot approach for the preparation of diblock copolymers consisting of polystyrene and polymyrcene blocks is described via a temperature-induced block copolymer (BCP) formation strategy. A monomer mixture of styrene and myrcene is employed. The unreactive nature of myrcene in a polar solvent (tetrahydrofuran) at -78°C enables the sole formation of active polystyrene macroinitiators, while an increase of the temperature (-38°C to room temperature) leads to poly(styrene-block-myrcene) formation due to polymerization of myrcene. Well-defined BCPs featuring molar masses in the range of 44-117.2kgmol-1 with dispersities, Ð, of 1.09-1.21, and polymyrcene volume fractions of 30-64% are accessible. Matrix assisted laser desorption ionization-time of flight mass spectrometry measurements reveal the temperature-controlled polymyrcene block formation, while both transmission electron microscopy and small-angle X-ray scattering measurements prove the presence of clearly microphase-separated, long range-ordered domains in the block copolymers. The temperature-controlled one-pot anionic block copolymerization approach may be general for other terpene-diene monomers.

Nitroxide-mediated polymerization of styrene and limonene in the framework of synthesis of potentially functional polymers using naturally occurring terpenes

In the framework of synthesis of potentially functional macromolecules based on commodity polymers with naturally occurring compounds, the nitroxide-mediated polymerization of styrene with limonene was investigated here. Various ratios of styrene and limonene were used, and the incorporation of limonene in the final polymer was monitored. Results from benzoyl peroxide/TEMPO-initiated polymerization showed small incorporation of limonene in the polystyrene chains, while it was also involved in forming oligomers (such as dimers or trimers). The presence of limonene resulted in a reduction in polymer average molecular weight through chain transfer reactions. From the kinetic analysis, limonene was found to inhibit styrene thermal auto-polymerization at high temperatures, acting as a radical scavenger. Using TEMPO-functionalized polystyrene macroinitiators to initiate the polymerization, no limonene oligomers in the final product were observed. Finally, when polystyrene macroinitiators and limonene were reacted in the absence of styrene monomer, limonene moieties were identified in the final polymer, resulting thus in polystyrene functionalization. This functionalization can be extended to the synthesis of novel materials based on naturally occurring terpenes, considering the variety of structures that can be obtained by applying NMP.

Synthesis of Conjugated Rod–Coil Block Copolymers by RuPhos Pd-Catalyzed Suzuki–Miyaura Catalyst-Transfer Polycondensation: Initiation from Coil-Type Polymers

A novel coil-first/grafting-from approach was developed for the synthesis of conjugated rod–coil block copolymers using RuPhos Pd-catalyzed Suzuki–Miyaura catalyst-transfer polycondensation (SCTP). First, aryl iodide end-functionalized polystyrene (PS) was prepared as a macroinitiator for SCTP via atom transfer radical polymerization (ATRP) followed by sequential end-group modifications, azidation, and click reactions. Then, RuPhos Pd-catalyzed SCTP using the PS macroinitiator was carried out in the presence of N-methyliminodiacetic acid boronate-containing 3-hexylthiophene monomer (M1), and this afforded well-defined PS-block-poly(3-hexylthiophene) with excellent control and high yield. The scope of this method was successfully expanded to include poly(methyl acrylate)-, poly(methyl methacrylate)-, and poly(ethylene oxide)-block-poly(3-hexylthiophene) with controlled molecular weight and low dispersity. Further, the combination of the conventional rod-first and newly developed coil-first approaches facilitated the straightforward synthesis of a unique ABC-type rod–coil–rod triblock copolymer that was limitedly accessible by other methods. We believe that this efficient and readily accessible synthetic platform would be highly useful for the preparation of novel conjugated rod–coil block copolymers that can be applied in optoelectronics, battery engineering, and chemical sensing.

The Effect of Poly(ethylene glycol) (PEG) Length on the Wettability and Surface Chemistry of PEG-Fluoroalkyl-Modified Polystyrene Diblock Copolymers and Their Two-Layer Films with Elastomer Matrix.

Diblock copolymers composed of a polystyrene first block and a PEG-fluoroalkyl chain-modified polystyrene second block were synthesized by controlled atom transfer radical polymerization (ATRP), starting from the same polystyrene macroinitiator. The wettability of the polymer film surfaces was investigated by measurements of static and dynamic contact angles. An increase in advancing water contact angle was evident for all the films after immersion in water for short times (10 and 1000 s), consistent with an unusual contraphilic switch of the PEG-fluoroalkyl side chains. Such a contraphilic response also accounted for the retained wettability of the polymer films upon prolonged contact with water, without an anticipated increase in the hydrophilic character. The copolymers were then used as surface-active modifiers of elastomer poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS)-based two-layer films. The elastomeric behavior of the films was varied by using SEBS matrices with different amounts of polystyrene. Whereas the mechanical properties strictly resembled those of the nature of the SEBS matrix, the surface properties were imposed by the additive. The contraphilic switch of the PEG-fluoroalkyl side chains resulted in an exceptionally high enrichment in fluorine of the film surface after immersion in water for seven days.

Cationic Bottlebrush Polymers from Quaternary Ammonium Macromonomers by Grafting‐Through Ring‐Opening Metathesis Polymerization

AbstractCationic bottlebrush homopolymers are polymerized using a grafting‐through approach by ring‐opening metathesis polymerization (ROMP) to afford well‐defined polymers. Quaternary ammonium macromonomers (MMs) are prepared by quaternizing tertiary amine MMs synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The quaternary ammonium MMs undergo ROMP to target molecular weights (Mn = 30 000–100 000 g mol−1) and a low dispersity (Đ = 1.10–1.30). Halide‐ligand exchange between the third generation Grubbs catalyst (G3) and halide counter ions (bromide and iodide ions) of MMs changes the catalyst activity throughout ROMP, causing it to deviate from pseudo‐first order kinetic behavior; however, the polymerization still follows controlled behavior without significant catalyst termination. Increasing steric bulk of the MMs decreases the polymerization rate as well. Amphiphilic block copolymers are synthesized by sequential polymerization of quaternary ammonium MMs and polystyrene (PS) MMs. Using a PS macroinitiator affords block copolymers with lower Đ values as compared to the less active cationic macroinitiator.

Thermoplastic Elastomer Coated-Snsb As an Anode Electrode for Li-Ion Batteries

The demand for developing next generation Li-ion batteries (LIBs) with high energy density and long cycle life drives the research toward alternative electrode materials with larger specific capacities. Among the several materials proposed to replace graphite (372 mAh g-1) as an anode material, antimony (Sb) and tin (Sn) have long been considered as an attractive replacement due to their superior lithium storage capacities of 660 mAh g−1 and 994 mAh g−1, respectively 1, 2. Unfortunately, the electrochemical performance of these materials fades during cycling because of the electrical contact loss induced by large volume variations combined with the continuous growth of a solid electrolyte interphase (SEI) layer at the surface hindering the electron transfer. The use of multi-phase active materials, such as SnSb, instead of pure metals (Sn or Sb) has been used to limit the large volume change by reacting with Li+ at different stages during the charge and discharge process 1. Unfortunately, the alloying/dealloying reaction is still accompanied by a volume change which results in the loss of electrical contact with the active material, Sn agglomeration, and the formation of SEI film on the electrode surface leading to poor electrochemical performance 3, 4. In the present work, micron-sized SnSb coated with a thin thermoplastic elastomer (TPE) is investigated as anode electrode for LIBs. The high failure strain of TPE is a very desirable feature for rechargeable LIBs as it improves the lifetime of high specific capacity anode materials that undergo mechanical fractures induced by large volume variations. Accordingly, an elastomer showing high strain property and good adhesion to the surface of the active material has been designed. Highly rubbery PS-b-PHEA was synthesized by the nitroxide meditated polymerization (NMP) method using a specific polystyrene macroinitiator allowing the presence of long hydroxyethyl acrylate blocks. Figure 1a shows the discharge capacity vs cycle number for the non-coated SnSb and the PS-b-PHEA-coated SnSb cycled at C/10 (i.e. 0.0827 A g–1). It is clearly apparent that the PS-b-PHEA-coated SnSb has superior cyclability than the non-coated SnSb with a reversible capacity of 720 mAh g–1 obtained, whereas only 356 mAh g–1 was retained after 50 cycles for the non-coated SnSb electrode. The remarkable stable capacity is attributed to the elastomer polymer film at the surface of SnSb. Indeed, highly stretchable PS-b-PHEA is able to bear the mechanical stress caused by the large volume variations and thus maintains good quality at the electrode/electrolyte interface and the inter-grains electronic percolation pathways during successive charging and discharging of the battery as well as the limiting the continuous growth of the SEI. Moreover, excellent capacity reversibility was achieved when cycled at fast kinetics (Figure 1b) and multiple C-rates (Figure 1c) confirming the strong protection role of the polymer. The advanced chemical and mechanical properties of PS-b-PHEA open up promising perspectives to significantly improve the electrochemical performance of all electrodes that are known to suffer from large volume variations. Figure 1. Discharge capacity versus the cycle number for PS-b-PHEA-coated SnSb and non-coated SnSb at a rate of (a) C/10 over 50 cycles and (b) 1C over 100 cycles, (c) cycling performance of PS-b-PHEA-coated SnSb at multiple C-rates. References M. Wachtler, J. O. Besenhard and M. Winter, J. Power Sources, 2001, 94, 189-193. P. Antitomaso, B. Fraisse, M. Sougrati, F. Morato-Lallemand, S. Biscaglia, D. Aymé-Perrot, P. Girard and L. Monconduit, J. Power Sources, 2016, 325, 346-350. A. T. Tesfaye, Y. D. Yücel, M. K. S. Barr, L. Santinacci, F. Vacandio, F. Dumur, S. Maria, L. Monconduit and T. Djenizian, Electrochimica Acta, 2017, 256, 155-161. L. Ji, M. Gu, Y. Shao, X. Li, M. H. Engelhard, B. W. Arey, W. Wang, Z. Nie, J. Xiao and C. Wang, Adv. Mater. , 2014, 26, 2901-2908. Figure 1

Superior Electrochemical Performance of Thin-Film Thermoplastic Elastomer-Coated SnSb as an Anode for Li-ion Batteries

The high failure strain of thermoplastic elastomers (TPEs) is a very desirable feature for rechargeable Li-ion batteries by improving the lifetime of high specific capacity anode materials that undergo mechanical fractures induced by large volume variations. In this work, poly(styrene-b-2-hydroxyethyl acrylate) called PS-b-PHEA was synthesized by a nitroxide meditated polymerization method. Owing to the use of a specific polystyrene macroinitiator (SG1), a suitable TPE copolymer with long hydroxyethyl acrylate blocks to ensure good mechanical properties is obtained for the first time. We show that the electrochemical properties of the PS-b-PHEA-coated SnSb anode are drastically improved by suppressing the crack formation at the surface of the electrode. Indeed, electrochemical characterization revealed that a high and stable gravimetric capacity over 100 cycles could be achieved. Moreover, excellent capacity reversibility was achieved when cycled at multiple C-rates and fast kinetics confirming the strong protection role of the polymer. The advanced chemical and mechanical properties of PS-b-PHEA open up promising perspectives to significantly improve the electrochemical performance of all electrodes that are known to suffer from large volume variations.

ARGET‐ATRP using β‐CD as reducing agent for the synthesis of PMMA‐b‐PS‐b‐PMMA triblock copolymers

ABSTRACTWe studied the role of β‐cyclodextrin (CD), a polyhydroxy cyclic sugar as reducing agent (RA) for the copper mediated activators regenerated by electron transfer atom transfer radical polymerization (ATRP) with the successful chain extension of methyl methacrylate blocks on the bifunctional polystyrene macroinitiator (PS‐MI) using nonaqueous solvent system for the first time. The PS‐MI was prepared by ATRP, had a polydispersity of 1.05 and gave triblock copolymers in the presence of β‐CD. We found that alcoholic groups of β‐CD show provisional reducing character and in situ convert Cu(II) to Cu(I) during polymerization. A well‐defined triblock copolymer with narrow molecular weight distribution (polydispersity index < 1.5) was obtained at 100 °C. The molecular weight of the block copolymers increased linearly with monomer conversion and the reaction showed good control over the molecular weights when compared to the theoretical values. We show that the mild reducing power of β‐CD is retained in a nonaqueous solvent also and is efficient with catalyst/RA ratio of 1:0.5. The effect of temperature on the reducing competency of β‐CD was evaluated and found to be active at around 80 °C even though its melting temperature is 290 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47117.

Analysis of Curing Rates of Adhesive Compositions Based on Methyl Methacrylate or Styrene and Macroinitiators, Obtained by Radically Initiated Polymerization with the Participation of Metallocenes

Reaction mixtures have been proposed as a basis of adhesive composition for gluing items made of poly(methyl methacrylate) or polystyrene. This composition consists of respective monomers and macroinitiators formed during radically initiated polymerization in the presence of metallocenes. An evaluation of the macroinitiators activity was carried out in postpolymerization of styrene and methyl methacrylate processes (the poly(methyl methacrylate) and polystyrene macroinitiators were considered, they were obtained in two different ways: the first one is during the polymerization with benzoyl peroxide or azobisisobutyronitrile and ferrocene or titanocene dichloride, and the second one is macroinitiators obtained in situ under the influence of UV radiation and in the presence of ferrocene or titanocene dichloride). The optimal methods of preparation and recipe of adhesive compositions were determined from the point of view of the fastest curing rate.

Micellisation of polystyrene-b-polyglycidol copolymers in water solution

The preparation of a set of amphiphilic polystyrene-b-polyglycidol (PS-b-PGL) diblock copolymers and their characteristics in aqueous media are described. The copolymers were prepared via anionic polymerisation starting from the synthesis of a polystyrene macroinitiator terminated by ethylene oxide, followed by anionic polymerisation of glycidol 1-ethoxyethyl ether to obtain a poly(1-ethoxyethyl glycidyl ether) block. The ethoxyethyl blocking groups of the hydroxyls were subsequently removed by hydrolysis. The copolymers differed in polymerisation degree of the polyglycidol block with DP values equal to 13, 43, 68 and 125, whereas the DP of polystyrene was 29. Two different organic media, N,N-dimethylformamide and dioxane, were used to prepare copolymer solutions dialysed afterward against water. The behaviour of diblock copolymers in water, their self-assembly and the size parameters of their aggregated structures were determined using dynamic light scattering. The critical micelle concentration (CMC) did not depend on the initial solvent and linearly increased with increasing content of hydrophilic glycidol units in the copolymer chain. However, above the CMC, the dispersions obtained from DMF contained a significant fraction of large aggregates. In the case of dioxane after dialysis, only one population of particles of the sizes, which can be related to typical core–shell micelles, was observed. Cryogenic transmission electron microscopy images revealed the presence of spherical objects and confirmed their sizes. PS-b-PGL micelles were highly stable and did not dissociate even after dissolution of their dispersions to concentrations below the CMC.

Bidirectional metal‐free ROMP from difunctional organic initiators

Bidirectional metal‐free ROMP from difunctional organic initiators

Synthesis of midblock-quaternized triblock copolystyrenes as highly conductive and alkaline-stable anion-exchange membranes

N,N-Diethyl-3-(4-vinylphenyl) propan-1-amine (DVPPA), a new monomer bearing a trialkyl amine group, provides versatile functionality to polystyrene (PS) PSm-PDVPPA2n-PSm triblock copolymers. A controlled synthetic strategy minimized chain transfer reactions while enabling the preparation of high molecular weight ABA triblock copolymers with relatively narrow (1.30–1.35) polydispersity indexes (PDIs) via reversible addition–fragmentation chain transfer (RAFT) polymerization between the DVPPA monomer and a difunctional PS macroinitiator. The presence of a tertiary amine functionality and its quaternized derivatives in the central blocks of the triblock copolymers afforded midblock-quaternized triblock co-PSs bearing pendent quaternary ammonium groups. These groups linked to the aromatic backbone with an alkyl spacer chain (3 carbon atoms) serving as steric hindrance shielding ionic centers. This polymer electrolyte with a “side-chain-type” polymer structure was designed by combining phase-separation architecture domains (confirmed by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM) analyses) and a crosslinking strategy with the aim to improve both the mechanical and alkaline stability properties. The side chain of this type of polyelectrolyte was incorporated by one quaternary ammonium group terminated with or without a crosslinkable unsaturated bond. After being simply heated at 80 °C for more than 18 h, crosslinked anion-exchange membranes (AEMs) exhibited enhanced tensile strength values (23.8–20.7 MPa) several times higher than those of conventional AEMs. An ionic conductivity of 26.1 mS cm−1 combined with low water uptake (16.5%) and swelling ratio (7.4%) values were achieved at room temperature for highly crosslinked membranes. Moreover, the membranes retained approximately up to 93.0% of their initial high hydroxide conductivity after the alkaline stability test (10 M aqueous NaOH, 80 °C, 20 d), thereby indicating excellent alkaline stability. Furthermore, in view of the good dimensional stability and satisfying mechanical properties of the resulting membranes, this approach that combines phase-separation architectures and crosslinking perfectly overcomes the obstacles blocking the development of AEMs, thereby having a great potential for practical applications.

Ordered Porous Films Prepared by the Breath Figure Method Based on Polystyrene-<em>b</em>-polyacrylonitrile

Ordered porous films were prepared by the breath figure method based on self-synthetic polystyrene-b-polyacrylonitrile (PS-b-PAN). Their morphologies were characterized by scanning electron microscopy. The influence of polymer concentration, solvent, and polymer structure on the structures of porous films was investigated. Film surfaces were covered with round hexagonally packed pores, and a honeycomb structure resided under film surfaces. With increasing polymer concentration in the chloroform (CHCl3) solvent, pore spacing increased and the size of honeycomb structure decreased. Multilayer structures were observed at higher concentration. When better volatile carbon disulfide (CS2) was instead used as the solvent, even highly ordered porous films were produced. Pore diameter and pore spacing increased, and the size of the honeycomb structure decreased. When the polystyrene macro-initiator (PS-Cl) without PAN blocks was adopted as the film material, nest-like structures instead of pores were formed on the film surface. The halo on the film surface suggests that when water droplets were positioned under the liquid film, defects formed on the film surface.

High molar mass segmented macromolecular architectures by nitroxide mediated polymerisation

A straightforward synthetic pathway based on nitroxide mediated polymerisation (NMP) for the synthesis of a variety of high molar mass segmented copolymers comprising both polystyrene (PS) and polyether segments is reported. First, various precursors such as linear or star-shaped polyether macromonomers, containing either α-methylstyrene or styrene functions at one polymer terminus, as well as PS and polyether macroalkoxyamines bearing either 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) or N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide (SG1) end-groups, were prepared. In a second step, these prepolymers were used to design different copolymer architectures such as block, graft, star-grafted, toothbrush and palm tree structures, in which PS constituted the backbone and polyether the side chains. Block copolymers were obtained by NMP of styrene initiated with polyether macroalkoxyamines. Copolymerisation of styrene with linear and star-shaped polyether macromonomers by NMP resulted in graft and star-grafted copolymers, respectively. A toothbrush copolymer was produced in a similar way with the exception of the initiator, which was a PS macroalkoxyamine. Likewise, palm tree architectures were obtained by homopolymerising polyether macromonomers initiated by PS macroinitiators. Advanced characterisation of the different polymer structures was performed, including 2D chromatography.

Synthesis and characterization of BAB and CBABC tri- and PentaBlock copolymers via atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) technique was applied successfully for the synthesis of poly(n-butyl methacrylate-b-styrene-b-n-butyl methacrylate) (PBMA-b-PS-b-PBMA), (BAB) and poly(methyl methacrylate-b-n-butyl methacrylate-b-styrene-b-n-butyl methacrylate-b-methyl methacrylate) (PMMA-b-PBMAb- PS-b-PBMA-b-PMMA), (CBABC) linear tri- and pentablock copolymers, respectively, in solution for the first time. Difunctional polystyrene macroinitiator that contains a bromide end-group was prepared by ATRP of styrene with dimethyl-2,6-dibromoheptanedioate (DMDBHD). The formation of block copolymers was confirmed by gel permeation chromatography (GPC), nuclear magnetic resonance (1H NMR) spectroscopy, and differential scanning calorimetry (DSC). Good agreement was observed between the theoretical and experimental molecular weights. The molecular weight distribution (MWD) was narrow and did not change much with the progress of the reaction. A linear increase in the number average molecular weight (M n ) with conversion was observed indicating that the polymerizations followed a ‘living’/controlled process. Both BAB and CBABC block copolymers showed core-shell type flower-like micellar structures when toluene is used as a selective solvent for A block (polystyrene). Open image in new window

Scanning Electron Microscopy Investigation of Molecular Transport and Reactivity within Polymer Brushes

Scanning electrochemical microscopy (SECM) allows investigation of the transport of redox probes within polymer brushes grown by atom-transfer radical polymerization (ATRP) from gold electrodes. By combination with cyclic voltammetry, the permeation of aqueous or organic redox probes is described and quantified in poly(glycidyl methacrylate) (PGMA) and polystyrene (PS). It is related to the chemical nature of both the probe and its environment (the solvent and the polymer phases). This study anticipates the permeation of reactive species within polymer brushes for further etching. The SECM reductive etching of the terminal C-Br bond of PGMA or PS macroinitiator layers is then investigated for different polymer thicknesses. The incomplete reductive etching of the macroinitiator layers is in agreement with the low permeability of the etchant within such polymer brushes and with the distribution of the terminal C-Br bonds throughout the brush. SECM proves to be a convenient tool for patterning such macroinitiator surfaces to form channels in block-copolymer structures. The combination of both analytical and patterning investigations enables one to anticipate and understand the reactivity of grafted macromolecules.

Lectin Recognizable Biomaterials Synthesized via Nitroxide-Mediated Polymerization of a Methacryloyl Galactose Monomer

The preparation of poly(2-(2′,3′,4′,6′-tetra-O-acetyl-β-d-galactosyloxy)ethyl methacrylate-co-styrene) (P(AcGalEMA-co-S)) glycopolymer was performed via nitroxide-mediated polymerization using a methacrylic acid-based alkoxyamine with N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) (SG1) nitroxide as mediating agent. In the presence of a low proportion of styrene, the polymerization of the glycomonomer was conducted in a controlled fashion at 85 °C. The synthesis of the diblock copolymers was investigated via two routes by using either P(AcGalEMA-co-S) or polystyrene macroinitiators capped with SG1 nitroxide to yield P(AcGalEMA-co-S)-b-PS and PS-b-P(AcGalEMA-co-S), respectively. The AcGalEMA moieties on the diblock copolymer were deacetylated to afford carbohydrate-based amphiphilic diblock copolymer, polystyrene-block-poly(2-(β-d-galactosyloxy)ethyl methacrylate-co-styrene) (PS-b-P(GalEMA-co-S)). The self-assembling properties of PS-b-P(GalEMA-co-S) amphiphilic diblock copolymers were thoroughly exploited to obtain micellar structures and porous films. Lectin binding assays were conducted using the UV−vis spectroscopy and dynamic light scattering to test the biofunctionality of the β-galactose moieties with peanut agglutinin (PNA) on the micelles. The polymer was used to prepare honeycomb structured porous films with bioactivity. Fluorescent PNA was eventually conjugated with the sugar moieties on the porous films. Most protein was conjugated to glycopolymer inside the pore, demonstrating that this procedure can be a simple route to pattern proteins onto surfaces.