Cyclic Polystyrene Research Articles

Interfacial and topological effects on the glass transition in free-standing polystyrene films.

United-atom molecular-dynamics computer simulations of atactic polystyrene (PS) were performed for the bulk and free-standing films of 2 nm-20 nm thickness, for both linear and cyclic polymers comprised of 80 monomers. Simulated volumetric glass-transition temperatures (Tg) show a strong dependence on the film thickness below 10 nm. The glass-transition temperature of linear PS is 13% lower than that of the bulk for 2.5 nm-thick films, as compared to less than 1% lower for 20 nm films. Our studies reveal that the fraction of the chain-end groups is larger in the interfacial layer with its outermost region approximately 1 nm below the surface than it is in the bulk. The enhanced population of the end groups is expected to result in a more mobile interfacial layer and the consequent dependence of Tg on the film thickness. In addition, the simulations show an enrichment of backbone aliphatic carbons and concomitant deficit of phenyl aromatic carbons in the interfacial film layer. This deficit would weaken the strong phenyl-phenyl aromatic (π-π) interactions and, hence, lead to a lower film-averaged Tg in thin films, as compared to the bulk sample. To investigate the relative importance of the two possible mechanisms (increased chain ends at the surface or weakened π-π interactions in the interfacial region), the data for linear PS are compared with those for cyclic PS. For the cyclic PS, the reduction of the glass-transition temperature is also significant in thin films, albeit not as much as for linear PS. Moreover, the deficit of phenyl carbons in the film interface is comparable to that observed for linear PS. Therefore, chain-end effects alone cannot explain the observed pronounced Tg dependence on the thickness of thin PS films; the weakened phenyl-phenyl interactions in the interfacial region seems to be an important cause as well.

Suppression of the Fragility-Confinement Effect via Low Molecular Weight Cyclic or Ring Polymer Topology

We used differential scanning calorimetry and spectroscopic ellipsometry to measure the molecular weight (MW) dependence of bulk fragility (mbulk) and spectroscopic ellipsometry to measure the thickness dependences of the glass transition temperature (Tg) and fragility (m) in supported thin films of low MW cyclic or ring polymer. The effects of confinement on Tg and m of thin polymer films are important in a range of advanced technology applications, including nanoimprinting. It has previously been shown that nanoconfined films of high MW linear polystyrene (PS) exhibit major Tg- and m-confinement effects whereas films of low MW cyclic PS (c-PS) show at most a very weak Tg-confinement effect. In the absence of chain ends, c-PS exhibits very weak Tg,bulk– and mbulk–MW dependences compared to linear PS. Despite low MW c-PS having mbulk values similar to that of high MW linear PS, we found that low MW c-PS films show a very weak m-confinement effect because of a weak free-surface effect; e.g., m for a 27 nm ...

Confinement Effects with Molten Thin Cyclic Polystyrene Films.

The surface fluctuations of a melt film of a low molecular weight cyclic polystyrene (CPS) manifest confinement effects for a film thickness (14Rg) much larger than that for which a melt film of the linear chain analog manifests confinement. This is true both in terms of absolute thickness and thickness relative to chain size, Rg. In fact, the linear analog polymer does not manifest confinement effects even at a thickness of 7Rg. Both types of films have a strongly adsorbed layer at the substrate that plays a role in slowing the surface fluctuations for the thinnest films. This layer is 70% thicker for the cyclic chains than for the linear chains. At the interface with the substrate the packing of the cyclic chains is perturbed much more strongly than is the packing of the linear chains.

Surface enrichment driven by polymer topology

We report a molecular dynamics simulation study of free-standing films of a blend of linear and cyclic polymer chains. We find that the composition of linear chains at the interface is enhanced relative to their bulk value for short chains but is depleted for long chains. Our findings are in agreement with recent experimental evidence reported for blends of short linear and cyclic polystyrene chains and highlight the genuine surface behavior in the short chain-length regime where theoretical predictions are more difficult. We highlight surface enrichment at low-energy surfaces as the result of competition between different entropic and enthalpic contributions to the interfacial free energy of the system.

Diselenide-Labeled Cyclic Polystyrene with Multiple Responses: Facile Synthesis, Tunable Size, and Topology.

Diselenide-containing polymers have attracted more and more attention due to their redox sensitivity and bioapplication. In this work, a bifunctional diselenocarbonate is prepared and used to mediate the reversible addition-fragmentation chain transfer (RAFT) polymerization, producing α,ω-selenocarbonate-labeled telechelic polystyrene. Based on effective aminolysis of the terminal selenocarbonates and the followed spontaneous oxidation coupling reaction of diselenols, monoblock cyclic polystyrene linked by one diselenide bond and multiblock cyclic copolymer linked by several diselenide bonds are prepared by manipulating the concentration of α,ω-telechelic polystyrene in solution. The progress of aminolysis and the subsequent spontaneous oxidation of selenols to diselenides are monitored by UV-vis, gel permeation chromatography (GPC), and NMR characterizations, confirming the cyclic topologies of the resultant polymers (monocyclic or multiblock cyclic polymer). The monoblock cyclic or multiblock polymers show redox sensitivity, which can be converted to linear polymer by reducing or oxidizing agent. Moreover, the obtained monoblock cyclic polymer or multiblock cyclic copolymer can be transformed to each other under UV irradiation by adjusting the concentration of the cyclic polystyrene. For the first time, this work provides an alternative and promising approach to realize the topological transformation of polymers by installing multiresponsive diselenide moities into the backbone of cyclic polymer.

The synthesis and photoactive properties of cyclic amphiphilic polymers with azobenzene in main chain

ABSTRACTThe cyclic amphiphilic polymers with azobenzene in main chain, cyclic azobenzene tetraethylene glycol polystyrene (cyclic‐Azo‐TEG‐PS) with different molecular weights, were successfully synthesized by combining atom transfer radical polymerization (ATRP) and Cu (I)‐catalyzed azide/alkyne cycloaddition (CuAAC). Gel permeation chromatography (GPC), proton nuclear resonance (1H NMR), Fourier transform‐infrared (FT‐IR), and matrix‐assisted laser desorption/ionization time of flight (MALDI‐TOF) mass spectrometry were used to prove the complete conversion from linear polymers to cyclic ones. The thermal properties and photoisomerization behaviors of obtained cyclic polymers have been investigated by comparison with the linear analogues. The cyclic polymer displayed a higher glass transition temperature compared with the linear one, measured by differential scanning calorimetry (DSC). It was found that the trans‐to‐cis and cis‐to‐trans isomerization of cyclic polymers was both slower than that of their respective linear counterparts upon irradiation by UV/visible light. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1834–1841

Interfacial diffusion of a single cyclic polymer chain.

Lateral diffusion of cyclic polystyrene at the interface between fused silica and dichloromethane is investigated at the single-molecular level. Narrowly distributed cyclic polystyrene (c-PS) of high purity with molecular weights spanning nearly an order of magnitude is prepared via atom transfer radical polymerization (ATRP) and Cu-catalyzed azide/alkyne cycloaddition (CuAAC) click reaction. The diffusion coefficients (D) of c-PS and its linear analogue (l-PS) on the surface are measured by fluorescence correlation spectroscopy (FCS). The diffusion coefficient of c-PS is discovered to have an inverse dependence on molecular weight, D ∼ M-1, in contrast to the case of linear polystyrene, which reproduces a stronger molecular weight dependence, D ∼ M-3/2. The slower interfacial motion of cyclic chains is attributed to their stronger binding to the surface and more importantly, the unique surface diffusion mechanism due to the absence of free chain ends.

Synthesis of diverse cyclic-brush polymers with cyclic polystyrene as a universal template via a grafting-from approach

With cyclic poly(styrene) as a universal template, facile synthesis of diverse cyclic-brush polymers via a grafting-from approach was illustrated.

Efficient synthesis of well-defined cyclic polystyrenes using anionic polymerization, silicon chloride linking chemistry and metathesis ring closure

An efficient method for the synthesis of well-defined cyclic polystyrenes using anionic polymerization, silicon chloride linking chemistry, and metathesis ring closure has been developed.

Synthesis and Characterization of Coumarin-Containing Cyclic Polymer and Its Photoinduced Coupling/Dissociation.

Cyclic polystyrene (PS) with a pendant coumarin group is prepared by the combination of atom transfer radical polymerization and "click" chemistry. Fluorescence resonance energy transfer process is observed in the fluorescence measurement of coumarin-containing PS, and cyclic PS exhibits stronger emission than that of its linear precursor. When cyclic PS is irradiated under UV light at λ = 365 nm, 8-shaped PS is achieved due to the dimerization of pendant coumarin group. Subsequently, 8-shaped PS can be divided into single macrocycle under UV irradiation at λ = 254 nm via the photocleavage of coumarin dimer. The photoinduced coupling and dissociation are monitored by UV/vis spectra and gel permeation chromatography (GPC).

Synthesis of graft copolymer with pendant macrocycles via combination of ATRP and click chemistry

Graft copolymers with pendant macrocycles were synthesized via “graft onto” method. First, cyclic polystyrene (PS) was achieved by the combination of atom transfer radical polymerization (ATRP) and Cu-catalyzed azide–alkyne cycloaddition (CuAAc), and then an alkynyl group was introduced to cyclic PS. Meanwhile, poly(3-azide-2-hydroxypropyl methacrylate) (PGMA-N3) was synthesized by ATRP of glycidyl methacrylate (GMA) and successive ring-opening of pendant epoxide ring with NaN3. The graft copolymer was achieved by the following click reaction between PGMA-N3 and alkynyl-containing cyclic PS. GPC and 1H NMR were utilized to characterize the obtained graft copolymers, and a maximal grafting density of 20% was observed. Thermal behaviors of linear PS, cyclic PS and PGMA grafted with cyclic PS (PGMA-g-cPS) were investigated by differential scanning calorimeter (DSC), and Tg of PGMA-g-cPS is higher than those of linear and cyclic PS.

環状及び線状高分子の界面物質拡散現象に関する研究

Diffusion of cyclic and linear polymers at interfaces was studied. Interdiffusion of cyclic polystyrene/cyclic deuterated polystyrene was measured by dynamic secondary ion mass spectroscopy as functions of temperature and molecular weight. Diffusion coefficient of cyclic polystyrene with weight-average molecular weight of 113k is twice as large as that of the corresponding linear one at all the temperatures employed. This result clearly shows that both the linear and cyclic polystyrenes have the same temperature dependence of segmental frictional coefficient. At an iso-free volume condition, diffusion coefficient of cyclic polystyrene is larger than that of the linear one at a given molecular weight. The short-time interdiffusion at an interface of linear polystyrene / linear deuterated polystyrene having different molecular weights was examined by time-resolved neutron reflectivity measurements. The model scattering length density profiles obtained by solving a partial differential equation for the diffusion process were used to analyze the data. The results indicate that even though the molecular weights of both components are larger than the critical molecular weight for entanglement, the initial interfacial broadening of bilayer films with different molecular weight proceeds with asymmetric mobility being inversely proportional to the molecular weight.

Glass Transition Temperature of Cyclic Stars.

Cyclic homo- and diblock copolymers with different topologies were synthesized using a combination of "living" radical polymerization and "click" coupling reactions. The topologies included 2- and 3-arm stars, with the arms consisting of either cyclic or linear polystyrene. In addition, a diblock consisting of a cyclic polystyrene and a cyclic poly(acrylic acid) was also made. The topologies by imposing topological constraints due to the presence of cyclic polymers and branch points had a marked influence on the glass transition temperature (Tg). It was found that for the polystyrene topology series, the Tg increased above the glass transition temperature at infinite molecular weight for a linear chain (i.e., Tg∞) and correlated to the more compact nature of cyclic polymers. For the cyclic diblock of polystyrene and poly(acrylic acid), the Tg increased significantly due to separation of the blocks into their pure phases. This resulted in significant stretching of the chains and thus loss of conformation entropy.

Sequential “Click” Synthesis of “Nano-Diamond-Ring-like” Giant Surfactants Based on Functionalized Hydrophilic POSS/C60Tethered with Cyclic Polystyrenes

This paper reports the design and facile synthesis of a novel series of “nano-diamond-ring-like” giant surfactants composed of a functionalized hydrophilic polyhedral oligomeric silsesquioxane (such as dihydroxyl-functionalized DPOSS) or fullerene (such as carboxylic acid-functionalized AC60) head as the “diamond” and a hydrophobic, cyclic polystyrene (CPS) tail as the “ring”. The synthetic route combines several steps of “click-type” reactions, demonstrating highly efficient and modular features. Starting from a specifically designed initiator, trifunctional linear polystyrene (LPS) precursors bearing vinyl, bromo, and alkyne groups were prepared by atom transfer radical polymerization (ATRP). Upon the subsequent azidation of LPS, copper-catalyzed Huisgen [3 + 2] cycloaddition reaction was employed to afford vinyl-functionalized CPS ring in high yield and purity. The vinyl group was then subjected to the thiol–ene reaction to introduce an azide group onto the CPS, providing an azide-functionalized CPS (C...

High‐Efficiency Preparation of Macrocyclic Polymers via a Circulatory Extraction–Cyclization Strategy

AbstractTypically, intramolecular cyclization reactions need to be conducted at high dilution to avoid interchain coupling, which leads to the production of cyclic polymer at an extremely low output. Herein, a high‐efficiency Cu‐catalyzed azide/alkyne cycloaddition “click” synthesis of cyclic polystyrene (PS) and cyclic poly (methyl methacrylate) (PMMA) is reported via a circulatory technique of evaporation–condensation–extraction–inflow strategy by the utilization of elaborately designed equipment. High‐output cyclic PS (one batch, 0.71 g cyclic polymer from 1.0 g linear polymer loading) and cyclic PMMA (one batch, 0.62 g cyclic PMMA from 1.0 g linear polymer loading) are achieved. This promising preparation should be beneficial to the large‐scale application and research of cyclic polymers.magnified image

Roll-to-flat texturing system with infrared preheating for manufacturing a microfluidic device

In the present study, a roll-to-flat (R2F) texturing system with infrared preheating was developed and characterized for the purpose of massively producing thermoplastic microfluidic devices with the height of [email protected] A thermoplastic substrate preheated up to its glass transition temperature (Tg) by a halogen lamp was textured between a roll mold and a plane actuator. After texturing, the substrate could be immediately cooled down as the roll mold screened the substrate from the infrared heat source. In order to characterize the transcription performance of the developed R2F texturing system for [email protected] features, a parametric study was carried out based on the Taguchi method with four kinds of thermoplastic materials, cyclic olefin copolymer (COC), polycarbonate (PC), polymethylmethacrylate (PMMA), and polystyrene (PS), which are the most commonly used in manufacturing microfluidic devices. As an application example of the developed system, a microfluidic device having a serpentine microchannel was fabricated via R2F texturing and subsequent thermal bonding.

Direct observation and mutual diffusion of cyclic polymers

A cyclic polymer is one of the ideal model polymers with which to investigate the effects of chain topology on the physical properties of polymers. In this review, I summarize my recent work demonstrating that the chain structure of cyclic polymers can be directly observed by atomic force microscopy (AFM) and that the mutual diffusion of cyclic polymers is faster than that of corresponding linear ones. For direct evidence of the cyclic structure, isolated molecules of cyclic poly(sodium styrenesulfonate), which was derived from cyclic polystyrene, were observed by AFM. The mutual diffusion of cyclic polystyrene/cyclic deuterated polystyrene was investigated as a function of temperature and molecular weight by dynamic secondary ion mass spectroscopy. For the molecular weight of 113k, the mutual diffusion coefficient of cyclic polystyrene, DC, was approximately twofold larger than that of the corresponding linear polymer, DL, at all temperatures. Under an iso-free volume condition, the DC value was larger than the DL value for all the molecular weights. These results clearly show that the chain topology strongly affects the molecular motion of the whole chain. Isolated molecules of cyclic polymers were directly observed by atomic force microscopy. Interdiffusion of cyclic polystyrene/cyclic deuterated polystyrene bilayer films were investigated as functions of temperature and molecular weight by dynamic secondary ion mass spectroscopy.

Straightforward synthesis of functionalized cyclic polymers in high yield via RAFT and thiolactone–disulfide chemistry

An efficient synthetic pathway toward cyclic polymers based on the combination of thiolactone and disulfide chemistry has been developed. First, heterotelechelic linear polystyrene (PS) containing an α-thiolactone (TLa) and an ω-dithiobenzoate group was synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization, employing a newly designed TLa-bearing chain transfer agent (CTA). The subsequent reaction of this heterotelechelic polymer with an amine, which acts as a nucleophile for both the TLa and dithiobenzoate units, generated the α,ω-thiol-telechelic PS under ambient conditions without the need for any catalyst or other additives. The arrangement of thiols under a high dilution afforded single cyclic PS (c-PS) through an oxidative disulfide linkage. The cyclic PS (c-PS) disulfide ring formation was evidenced by SEC, MALDI-TOF MS and 1H-NMR characterization. Moreover, we demonstrated a controlled ring opening via either disulfide reduction or thiol–disulfide exchange to enable easy and clean topology transformation. Furthermore, to illustrate the broad utility of this synthetic methodology, different amines including functional ones were employed, allowing for the one-step preparation of functionalized cyclic polymers with high yields.

Differentiation of Linear and Cyclic Polymer Architectures by MALDI Tandem Mass Spectrometry (MALDI-MS2)

[M + Ag](+) ions from cyclic and linear polystyrenes and polybutadienes, formed by matrix-assisted laser desorption ionization (MALDI), give rise to significantly different fragmentation patterns in tandem mass spectrometry (MS(2)) experiments. In both cases, fragmentation starts with homolytic cleavage at the weakest bond, usually a C-C bond, to generate two radicals. From linear structures, the separated radicals depolymerize extensively by monomer losses and backbiting rearrangements, leading to low-mass radical ions and much less abundant medium- and high-mass closed-shell fragments that contain one of the original end groups, along with internal fragments. With cyclic structures, depolymerization is less efficient, as it can readily be terminated by intramolecular H-atom transfer between the still interconnected radical sites (disproportionation). These differences in fragmentation reactivity result in substantially different fragment ion distributions in the MS(2) spectra. Simple inspection of the relative intensities of low- versus high-mass fragments permits conclusive determination of the macromolecular architecture, while full spectral interpretation reveals the individual end groups of linear polymers or the identity of the linker used to form the cyclic polymer.

A convenient method for the synthesis of cyclic polymers by ATRP

Cyclic polystyrene and poly(methyl methacrylate) with narrow molecular weight distribution were synthesized conveniently by intra-molecular cyclization of α-carboxyl-ω-chloride hetero-telechelic polystyrene and poly(methyl methacrylate) using potassium carbonate as the catalyst in highly dilute solution, respectively. The linear precursors were prepared successfully by atom transfer radical polymerization (ATRP) using 4-(chloromethyl)benzoic acid as an initiator. The chemical structures and molecular weights of the synthesized polymers were systematically characterized by nuclear magnetic resonance spectrum (1 H-NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The results revealed that high purity cyclic polymers were synthesized via a combination of intra-molecular cyclization and ATRP, and isolated easily by column chromatography on silica gel using a mixture of petroleum ether /ethyl acetate as an eluant.