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Reversible-deactivation radical polymerization (RDRP) based on direct photolysis has a favorable reaction structure for superior controllability compared to that of conventional RDRP. However, this aspect has not been fully demonstrated because the photolysis process is vaguely understood. In this study, we propose a mechanism for photolysis and apply the proposed mechanism to obtain polyacrylates with an extremely narrow dispersity approaching the Poisson distribution (an ideal molecular weight distribution attained in living polymerization) and a negligible fraction of dead chains (< 2%), even for very high conversion (> 90%) and short reaction time (5 h). Based on the results, extremely well-defined and defect-free a,w-hydroxyl end-functionalized polyacrylates were prepared to utilize the resulting polyols as soft segments of thermoplastic polyurethane (TPU) elastomer. Using the prepared polyols, TPU elastomers that do not follow the conventional trade-off relationship of strength-elongation and robustness-self healing ability were successfully prepared, highlighting their potential as next-generation functional polymeric materials.

End group functionality is a key parameter of functional polymer chains. The end-capping efficiency of living polystyryl lithium with various epoxides, namely ethylene oxide (EO), ethoxy ethyl glycidyl ether (EEGE) and isopropylidene glyceryl glycidyl ether (IGG), is investigated with solvent gradient interaction chromatography (SGIC). Generally, end-capping efficiencies95% are observed. Hydroxy functional polystyrene (PS-OH, PS-EEGE-OH, and PS-IGG-OH) with molar masses ranging from 13.8 to 15.0 kg mol

Living and dead chains of a polystyrene synthesized by atom transfer radical polymerization were separated and characterized by high performance liquid chromatography (HPLC), size exclusion chromatography (SEC), NMR, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The bromine end group in the living chain was quantitatively converted to a hydroxyl end group via first azidation and subsequent copper-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction with propargyl alcohol. The living chains bearing a polar end group are fully resolved from the unmodified dead chains by HPLC separation using a bare silica stationary phase. Molecular weight distributions (MWD) of the living and dead chain are characterized by SEC and MALDI-MS. The MWD of the living chains is close to a Poisson distribution. Interestingly, the elution peak of the living chains in the HPLC separation split into two. The peak split is attributed to the diastereomeric structure of the chain end by NMR and MALDI-MS analyses.

Adding small amounts of ring polymers to a matrix of their linear counterparts is known to increase the zero-shear-rate viscosity because of linear-ring threading. Uniaxial extensional rheology measurements show that, unlike its pure linear and ring constituents, the blend exhibits an overshoot in the stress growth coefficient. By combining these measurements with ex-situ small-angle neutron scattering and nonequilibrium molecular dynamics simulations, this overshoot is shown to be driven by a transient threading–unthreading transition of rings embedded within the linear entanglement network. Prior to unthreading, embedded rings deform affinely with the linear entanglement network and produce a measurably stronger elongation of the linear chains in the blend compared to the pure linear melt. Thus, rings uniquely alter the mechanisms of transient elongation in linear polymers.

A new type of model branched polymer, asymmetric H-shaped polybutadienes, consisting of central crossbars having various combinations of short and long arms attached to the ends of the crossbars, was synthesized using living anionic polymerization and chlorosilane linking chemistry. The linking agent 4-(dichloromethylsilyl)diphenylethylene provides selective reactivity to attach short or long arms on one side or both sides as desired. The samples were characterized thoroughly by size exclusion chromatography with light scattering detection (SEC-LS) and found to exhibit controlled molecular weights, as well as narrow polydispersity indices (PDIs of 1.01–1.06). Temperature gradient interaction chromatography, a method with far superior resolution as compared to SEC, also shows that these materials are well-defined, with minimal and identifiable impurities.

We report on the unusual response of a well-characterized entangled comb polymer in simple shear flow. The polymer with highly entangled backbone (about 16 entanglements) and on average 29 long branches (about 3 entanglements each) has been extensively characterized by interaction chromatography and its rheology carefully studied under controlled conditions using a special cone partitioned-plate geometry. We observe that the start-up shear stress becomes roughly rate independent above a certain critical rate, related to the relaxation time of the branches. Within the rate-independent region, the start-up shear stress displays a double overshoot. We interpret these observations in light of tube-based pompom dynamics. The key idea is that for sufficiently long branches the main stress overshoot, which reflects backbone stretching and orientation, is preceded by the withdrawal of branches into the backbone tube. The excellent quantitative comparison between the simulations and experiments supports the proposed mechanism of the double stress overshoot.

We investigated the microphase in thin films of polystyrene-b-polyisoprene showing cylinder morphology to elucidate the orientation mechanism of the cylinder phase during solvent vapor annealing (S...

We present a comprehensive experimental rheological dataset for purified entangled ring polystyrenes and their blends with linear chains in nonlinear shear and elongation. In particular, data for the shear stress growth coefficient, steady-state shear viscosity, and first and second normal stress differences are obtained and discussed as functions of the shear rate, as well as molecular parameters (molar mass, blend composition, and decreasing molar mass of linear component in the blend). Over the extended parameter range investigated, rings do not exhibit clear transient undershoot in shear, in contrast to their linear counterparts and ring-linear blends. For the latter, the size of the undershoot and respective strain appear to increase with the shear rate. The universal scaling of the strain at overshoot and fractional overshoot (the ratio of the maximum to the steady-state shear stress growth coefficient) indicates subtle differences in the shear-rate dependence between rings and linear polymers or their blends. The shear thinning behavior of pure rings yields a slope nearly identical to predictions (−4/7) of a recent shear slit model and molecular dynamics simulations. Data for the second normal stress difference are reported for rings and ring-linear blends. While N2 is negative and its absolute value stays below that of N1, as for linear polymers, the ratio –N2/N1 is unambiguously larger for rings compared to linear polymer solutions with the same number of entanglements (almost by a factor of 2), in agreement with recent nonequilibrium molecular dynamics simulations. Furthermore, –N2 exhibits slightly weaker shear rate dependence compared to N1 at high rates, and the respective power-law exponents can be rationalized in view of the slit model (3/7) and simulations (0.6), although further work is needed to unravel the molecular original of the observed behavior. The comparison of shear and elongational stress growth coefficients for blends reflects the effect of ring-linear threading, which leads to significant viscosity enhancement in elongation. Along the same lines, the elongational stress is much larger than the first normal stress in shear, and their ratio is much larger for rings and ring-linear blends compared to linear polymers. This confirms the interlocking scenario of rings and their important role in mechanically reinforcing linear matrices.

We blend newly synthesized nearly monodisperse four-arm star 1,4-polybutadienes with various well-entangled linear polymers, confirming the conclusions in Desai et al. [ Macromolecules201649 (13)49...

We report on the chromatographic separation and characterization of living chains in polystyrene prepared by reversible addition–fragmentation chain-transfer (RAFT) polymerization. To achieve full ...

We report a method to directly introduce a hydroxyl group at the omega chain end of polystyrene prepared by atom-transfer radical polymerization. To achieve the quantitative conversion of the bromine group to a hydroxyl group, the transfer reaction of a carbocation with water was exploited. This transfer reaction is a well-known reaction in cationic polymerization. The quantitative conversion and chemical structures of the hydroxyl-terminated PS were characterized using 1H nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and high-performance liquid chromatography. In addition, alcohol-based compounds were used to introduce acetonide and propane groups into PS-Br. We introduce a facile method to convert the bromine end of the polymer into a hydroxyl group. For this, bromine-terminated polystyrene (PS-Br) was prepared by atom transfer radical polymerization. The bromine groups of the PS-Br could be directly converted to hydroxyl groups by using Ag+ as the Lewis acid in water/acetone. The conversion yield was investigated by 1H nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The morphology of well-purified triblock terpolymers was investigated by X-ray scattering and transmission electron microscopy after solvent vapor annealing (SVA) and compared with that developed a...

We present here a systematic investigation on the glass transition temperature (Tg) for a series of highly purified cyclic polystyrene (c-PS) samples with molecular weight (MW) varying from 3300 to 13,400. Compared with their linear counterparts, c-PS samples show much higher Tg and exhibit weak Tg-MW dependence. By blending linear polystyrenes with c-PS, the linear polymer contamination effect on the Tg of c-PS was systematically investigated. It was found that the measured Tg of the mixtures increases with the decrease of linear polymer content and the relationship is consistent with Fox equation. These results are helpful to understand the origin of previously reported different Tg-MW relationship for c-PS.

We determine experimentally the “dilution exponent” α for entangled polymers from the scaling of terminal crossover frequency with entanglement density from the linear rheology of three 1,4-polybutadiene star polymers that are blended with low-molecular-weight, unentangled linear 1,4-polybutadiene at various star volume fractions, ϕs. Assuming that the rheology of monodisperse stars depends solely on the plateau modulus GN(ϕs) ∝ ϕs1+α, the number of entanglements per chain Me(ϕs) ∝ ϕs–α, and the tube-segment frictional Rouse time τe(ϕs) ∝ ϕs–2α, we show that only an α = 1 scaling superposes the Me(ϕs) dependence of the terminal crossover frequency ωx,t of the blends with those of pure stars, not α = 4/3. This is the first determination of α for star polymers that does not rely on any particular tube model implementation. We also show that a generalized tube model, the “Hierarchical model”, using the “Das” parameter set with α = 1 reasonably predicts the rheological data of the melts and blends featured in...

Different types of polymer chains generated during the nitroxide-mediated polymerization of styrene are separated for the first time, and their molecular weight distribution (MWD) is investigated. Living and dead chains are monitored during the reaction; specifically, two types of living chains derived from the initiation of the alkoxyamine (RT) and the self-initiation of styrene and dead chains present in the as-prepared polystyrene (PS). To distinguish between each polymer species, different numbers of hydroxyl groups are introduced onto the T and R groups of the alkoxyamine (one and two groups, respectively). Each living and dead chains is resolved according to the distinct number of hydroxyl groups on its chain-end using high-performance liquid chromatography. Molecular structures of the fractionated PS are characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 1 H nuclear magnetic resonance spectroscopy, and the results of which show two distinct initiation paths: one originating from RT and the other from the self-initiation of styrene. Molecular weight and MWD are measured using size-exclusion chromatography and reveal a narrow MWD for the living chains derived from RT. Contrastingly, a broad and skewed MWD is observed for the other living chains derived from the self-initiation of styrene and the dead chains.

Size exclusion chromatography (SEC) is the most widely employed chromatographic separation technique for characterization of synthetic polymers. SEC separates polymer molecules according to their chain size utilizing size-dependent pore accessibility of polymer molecules. Since the polymer chain size depends on not only molecular weight (MW) but also other molecular characteristics such as composition, chain architecture, and microstructure, SEC cannot separate, for instance, nonlinear homopolymers according to MW or copolymers according to their composition. In contrast to SEC, interaction chromatography (IC) fractionates polymers according to the interaction strength between the polymer molecules and the sorbent. As a result, IC separation is sensitive to chemical nature and MW of polymers unlike the size-sensitive SEC. Furthermore, one can access to the chromatographic critical condition by adjusting the solute interaction strength with the sorbent until the exclusion and interaction contributions to the solute retention are exactly compensated. At the critical condition, polymers of different MW coelute. Therefore liquid chromatography (LC) at the critical condition (LCCC) is a unique tool for LC separation of polymers since the peak dispersion of polymers due to their MW distribution can be suppressed for effective analyses of other molecular characteristics. Recently, polymer separations using two-dimensional LC by various combinations of SEC, IC, or LCCC are increasingly used for the characterization of polymers with multivariate distributions. For effective IC separations, solute interaction strength needs to be controlled judiciously during the elution. For this purpose, either solvent gradient or temperature gradient elution is often used. In this chapter, principles and applications of IC and LCCC separation methods of synthetic polymers are reviewed with an emphasis on the temperature gradient elution method.

We combine linear viscoelastic measurements and modelling in order to explore the dynamics of blends of the same-molecular-weight ring and linear polymers in the regime of the low volume fraction (0.3 or lower) of the ring component. The stress relaxation modulus is affected by the constraint release (CR) of both rings and linear components due to the motion of linear chains. We develop a CR-based model of ring-linear blends that predicts the stress relaxation function in the low fraction regime of ring component in excellent agreement with experiments. Rings trapped by their entanglements with linear chains can only relax by linear-chain-induced constraint release, resulting in much slower relaxation of rings than of linear chains. The relative viscosity [Formula: see text] of the blend with respect to the linear melt viscosity η(L) at ring overlap volume fraction [Formula: see text] increases proportionally to the square root of ring molecular weight [Formula: see text]. Our experimental results clearly demonstrate that it is possible to enhance the viscosity and simultaneously the structural relaxation time of linear polymer melts by adding a small fraction of ring polymers. These results not only provide fundamental insights into the physics of the CR process but also suggest ways to fine-tune the flow properties of linear polymers by means of adding rings.

A polyring capable of reversible growth and dissociation is synthesized from a tricyclic polystyrene (PS) prepared by combining atom transfer radical polymerization of a 4-arm star-shaped PS and azide–alkyne click reactions. In the preparation of the tricyclic PS, a coupling agent containing a disulfide linkage is used in the click cyclization reaction. The reduction of the disulfide linkage in the tricyclic PS results in an 8-shaped PS with thiol groups which on oxidation leads to a high molecular weight polyring. The topology transformation between the polymers occurs via reversible redox reaction of disulfide/thiol. The high molecular weight of the polyring is realized due to the formation of flexible S–S linkage between the 8-shaped PSs. Their structures are confirmed by FT-IR, 1H NMR, SEC, and MALDI-TOF MS analyses. In addition, molecular weight control of the polyring according to polymer concentration has been confirmed through SEC analysis.

Cyclic polymers synthesized by ring-closure method from linear precursors contain some of linear contaminates. In this work, the origin of linear contaminates in cyclic polystyrenes ( c -PS) is demonstrated by the coupling of liquid chromatography at the critical condition (LCCC) with matrix-assisted laser desorption/ionization time-of-flight mass spectra. The linear contaminates are revealed to be the “dead” chains during ATRP by chain termination, the unreacted linear polystyrene ( l -PS) precursors, and the dimers by the imperfect ring-closure reaction. The c -PS are purified by LCCC fractionation, and the results show the LCCC fractionation at the critical adsorption point (CAP) of c -PS is more efficient than that at the CAP of linears for low molecular weight ( c -PS with high purity (>99.6%) via the tandem-coupled LCCC fractionation at the CAP of l -PS and at the CAP of c -PS.

The critical adsorption point (CAP) of linear and star-shaped polymers was investigated by normal phase and reversed phase liquid chromatography (NPLC and RPLC) and computer simulation. Three sets of polystyrenes (PS) differing in chain architecture and chemically distinct groups were prepared: linear PS (sec-butyl and hydrogen end group), 2-arm PS (linear, two sec-butyl end groups and one silyl group in the middle of the chain) and 4-arm star-shaped PS (four sec-butyl end groups and one silyl group in the center of the star). It was found that the column temperature at CAP, TCAP (linear PS) = TCAP (2-arm PS) > TCAP (4-arm PS) in both RPLC and NPLC which can be attributed to the variation in chain architecture. However, the elution times at CAP of three polymers are all different: In NPLC, tE,CAP (linear) > tE,CAP (2-arm PS) > tE,CAP (4-arm PS) while in RPLC, tE,CAP (4-arm PS) > tE,CAP (2-arm PS) > tE,CAP (linear). The variation of tE,CAP can be explained by the contribution of the chemically distinct gro...

Covalent fixed multicyclic polystyrene conformers were synthesized from inconvertible polystyrene conformers based on p-tert-butylthiacalix[4]arene by azidation and subsequent click coupling. Selective 1D NOESY analyses confirmed that the spatial structures of star polystyrene precursors and multicyclic polystyrenes were preserved during the azidation and click coupling processes. The conformation of star polymers affected degree of decrease in the hydrodynamic volume after cyclization but had little effect on glass transition behavior. The rigid core of star polymer increased the Tg but in the case of multicyclic polymer, this influence of core structure was reduced. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.

An exact polystyrene-graft-polyisoprene (PS-g-PI) synthesized by iterative anionic polymerization and graft reaction using diphenylethylene functional groups was characterized by liquid chromatography. As-prepared graft copolymer contains various byproducts other than the target PS-g-PI. After the fractionation by size exclusion chromatography (SEC), the PS-g-PI appears quite homogeneous by SEC analysis, but the temperature gradient interaction chromatography (TGIC) separation with respect to the PI branch number showed a significantly wide distribution in the number of PI grafts. The resolved TGIC peaks were fractionated, and the molecular weight of each block (backbone or branches) was estimated by liquid chromatography at critical condition (LCCC) analysis at the critical adsorption condition of the opposite block. The composition determined by LCCC analysis and 1H NMR analysis yielded a reasonably self-consistent result. Through this study, we demonstrated that SEC analysis of this type of branched co...

Size exclusion chromatography (SEC) coupled with triple detection (TD) method is widely used for branching analysis of polymers. However, there is an inherent limitation of SEC-TD method that SEC separates polymers according their hydrodynamic size. The SEC resolution of branched polymers is not high since the hydrodynamic size of branched polymers does not change as much as linear polymers with molecular weight (MW), let alone the serious band-broadening in SEC. As a solution of the problem, we propose temperature gradient interaction chromatography (TGIC)-TD method taking advantage of TGIC's characteristics of separating branched polymers according to their MW with much higher resolution than SEC. The potential of the method was demonstrated using regular star-shaped polybutadienes prepared by anionic polymerization. They were characterized by both SEC-TD and TGIC-TD methods. Detailed analysis of branch distribution was possible for narrow MW fractions in TGIC-TD while SEC-TD only provides with average branch number for SEC fractions.

In the melt state at equilibrium, entangled nonconcatenated ring macromolecules adapt more compact conformations compared to their linear analogs and do not form an entanglement network. We show here that, when subjected to uniaxial stretching, they exhibit a unique response, which sets them apart from any other polymer. Remarkably, whereas both linear and ring polymers strain-harden, the viscosity of the rings increases dramatically (the melt thickens) at very low stretch rates due to the unraveling of their conformations along the stretching direction. At high rates, stretching leads to viscosity thinning similar to that of entangled linear polymers, albeit with subtle differences.

We investigate the influence of the environment on the relaxation dynamics of well-defined H-polymers diluted in a matrix of linear chains. The molar mass of the linear chain matrix is systematically varied and the relaxation dynamics of the H-polymer is probed by means of linear viscoelastic measurements, with the aim to understand its altered motion in different blends, compared to its pure melt state. Our results indicate that short unentangled linear chains accelerate the relaxation of both the branches and the backbone of the H-polymers by acting as an effective solvent. On the other hand, the relaxation of the H-polymer in an entangled matrix is slowed-down, with the degree of retardation depending on the entanglement number of the linear chains. We show that this retardation can be quantified by considering that the H-polymers are moving in a dilated tube at the rhythm of the motion of the linear matrix.

The critical adsorption points (CAP) for ring and linear polymers are determined and compared using Monte Carlo simulations and liquid chromatography experiments. The CAP is defined as the coelution point of ring or linear polymers with different molecular weights (MW). Computational studies show that the temperature at the CAP, TCAP, for rings is higher than TCAP for linear polymers regardless of whether the chains are modeled as random walks or self-avoiding walks. The difference in the CAP can be attributed only to the architectural difference. Experimentally, four pairs of linear and ring polystyrenes (PS) of different MW were synthesized and purified. Care was taken to account for the difference between the end-groups in linear polymers and the linkage unit in ring polymers. Elution of these polymers using a C18 bonded silica stationary phase and a CH2Cl2/CH3CN mixed eluent were studied. The temperature at the coelution point, TCAP, and the coelution time at the CAP, tE,CAP, were determined for both ...

We report herein the effects of solvent, concentration, and molecular weight of α-alkynyl-ω-azido polystyrenes (l-PS-N3) on the synthesis of monocyclic polystyrenes (c-PS) by intra-chain coupling of l-PS-N3 via Cu-catalyzed azide/alkyne cycloaddition method. By using fully end-functionalized l-PS-N3 as precursors, the optimum cyclization conditions to synthesize high purity c-PS (>99% by SEC) are revealed, at concentrations around 7.9 μmol/L in DMF. The c-PS products are fully characterized by SEC, LCCC, 1H NMR, and MALDI-TOF Mass spectrometry. The yield of c-PS decreases with increment of concentration of l-PS-N3 as predicted by Jacobson and Stockmayer's equation. Interestingly, among the three studied PS samples with different molecular weight (∼4k, 9k, 14k Da), the medium one (PS9k) provides the best c-PS yield, while in the three studied solvent (toluene, DMF, cyclohexane), DMF gives the best yied. The results reveal that the PS chain conformation in the solution, which is affected by the solvent and molecular weights, plays an important role in the intra-chain cyclization reaction.

We compare predictions of two of the most advanced versions of the tube model, namely the “Hierarchical model” by Wang et al. [J. Rheol. 2010, 54, 223] and the BoB (branch-on-branch) model by Das et al. [J. Rheol. 2006, 50, 207], against linear viscoelastic G′ and G″ data of binary blends of nearly monodisperse 1,4-polybutadiene 4-arm star polymer of arm molar mass 24 000 g/mol with a monodisperse linear 1,4-polybutadiene of molar mass 58 000 g/mol. The star was carefully synthesized and characterized by temperature gradient interaction chromatography and by linear rheology over a wide frequency region through time–temperature superposition. We found large failures of both the Hierarchical and BoB models to predict the terminal relaxation behavior of the star/linear blends, despite their success in predicting the rheology of the pure star and pure linear polymers. This failure occurred regardless of the choices made concerning constraint release, such as assuming arm retraction in “fat” or “skinny” tubes....

Nonlinear polystyrenes (PS) with similar molecular weights but with different molecular structures having star-, figure-8-, and cage-shaped architectures were synthesized by combining atom transfer radical polymerization (ATRP) and click chemistry. Figure-8- and cage-shaped PS were fractionated by using a gradient normal phase liquid chromatography as confirmed by SEC-LS, MALDI–TOF MS, 1H NMR, and FT-IR spectrometry. Their purities were estimated by using a two-dimensional liquid chromatography (2D-LC). The glass transition temperatures of these topologically different polymers were in the order of cage-, figure-8-, and star-shaped polymers possibly due to the multiple links that constrain the overall molecular diffusivity in the case of multicyclic polymers (figure-8, and cage). Monte Carlo simulation on the glass transition behavior of model system also agreed well with the experimental results.

Poloxamers are low molar mass triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), having number of applications as non-ionic surfactants. Comprehensive one and two-dimensional liquid chromatographic (LC) analysis of these materials is proposed in this study. The separation of oligomers of both types (PEO and PPO) is demonstrated for several commercial poloxamers. This is accomplished at the critical conditions for one of the block while interaction for the other block. Reversed phase LC at CAP of PEO allowed for oligomeric separation of triblock copolymers with regard to PPO block whereas normal phase LC at CAP of PPO renders oligomeric separation with respect to PEO block. The oligomeric separation with regard to PEO and PPO are coupled online (comprehensive 2D-LC) to reveal two-dimensional contour plots by unconventional 2D IC×IC (interaction chromatography) coupling. The study provides chemical composition mapping of both PEO and PPO, equivalent to combined molar mass and chemical composition mapping for several commercial poloxamers.

It is commonly believed that cyclic polymers have smaller hydrodynamic radii (Rhs) than their linear counterparts due to the constraint topology. This consensus is based on the results from polymers with high molecular weights (MWs), where the chains are considered as coils. Herein, we investigate the Rhs of low MW cyclic polystyrenes (3000–11,000), cyclic alkanes and their linear counterparts by diffusion ordered NMR spectroscopy. For the first time, a non-free draining effect for small cyclics is revealed, due to the depletion of solvent molecules to pass through the rings, which leads to the increment of hydrodynamic size. With the decrement of polymer MW, this effect becomes more significant and Rhs of cyclic polystyrenes approach that of their linear counterparts. Below a crossover point at MW around 660, Rhs of cyclic polystyrenes are larger than their linear counterparts from the established scaling laws. This is supported by the observed phenomena that cycloalkanes have larger Rhs than their n-alkane counterparts. The results are helpful in understanding the thermodynamic behaviors of small cyclics in solution, especially those bioactive small ring molecules in life science.

The state‐of‐the‐art understanding of entangled linear polymers is based on the concept of physical network formation from entanglements. The physical network is characterized by aplateau modulus in linear viscoelastic (LVE) measurements. However, linking the two free ends of a linear polymer, thereafter called a ring polymer, has dramatic consequences. For example, non-concatenated rings have much lower zero‐shear‐rate viscosity compared to their linear entangled counterparts. A plateau modulus is not observed in LVE measurements for ring polymers [1].Due to the difficulties in synthesis, which leads to very limited amount of samples, well‐defined ring polymers have never been studied in extensional flow. In this work, we present the first results of extensional rheology of a ring polystyrene (PS) melt with the molecular weight 185k(Ring‐185k). We show that the ring PS is surprisingly strain hardening in extensional flow, and reaches the same extensional steady state viscosity as its linear counterpart (Lin‐185k) when the stretch rate is fast enough. We further present the extensional rheology of blends made of Ring‐185k and Lin‐185k, with weight fraction of 5%, 20%, and 30% of Ring‐185k, respectively. We show that in the transient stress‐strain responses, stress overshoot is observed for the samples containing 20% and 30% Ring‐185k, while the stress overshoot is not observed for the pure Ring‐185k and Lin‐185k.The present results shed light into the fascinating flow properties of polymers without free ends, while they also advance the state‐of‐the‐art in polymer physics. At the same time, they open the route for understanding the response of folded proteins and chromosome territories under strong external fields.

The intrinsic viscosity of cyclic polystyrenes (C-PS) and linear polystyrenes (L-PS) with molecular weight (MW) ranging from 16K to 370K was measured in THF using size exclusion chromatography coupled with a triple detection system. The C-PS samples were prepared by a ring-closure reaction of telechelic linear precursor synthesized by anionic polymerization. As-synthesized C-PS samples after the ring-closure reaction contain various byproducts, and they were fractionated by liquid chromatography at the critical condition to obtain highly pure C-PS. While the intrinsic viscosity of L-PS agrees well with the literature data, C-PS shows significantly lower value than the literature values. The Mark–Houwink exponent of C-PS is 0.67, somewhat lower than 0.70 for L-PS in the good solvent over the MW range examined. Therefore, the ratio of the intrinsic viscosity of C-PS to L-PS (g′ = [η]C/[η]L) in THF is not MW independent but decreases as MW increases (0.63 ≥ [η]C/[η]L ≥ 0.57). The trend of intrinsic viscosity agrees well with the computer simulation result. The discrepancy in [η]C from the literature values can largely be attributed to the contamination of linear byproducts in the earlier studies.

A detailed characterization of a commercial polystyrene/polybutadiene block copolymer material (Styrolux) was carried out using two-dimensional liquid chromatography (2D-LC). The Styrolux is prepared by statistical linking reaction of two different polystyrene- block-polybutadienyl anion precursors with a multivalent linking agent. Therefore, it is a mixture of a number of branched block copolymers different in molecular weight, composition, and chain architecture. While individual LC analysis, including size exclusion chromatography, interaction chromatography, or liquid chromatography at critical condition, is not good enough to resolve all the polymer species, 2D-LC separations coupling two chromatography methods were able to resolve all polymer species present in the sample; at least 13 block copolymer species and a homopolystyrene blended. Four different 2D-LC analyses combining a different pair of two LC methods provide their characteristic separation results. The separation characteristics of the 2D-LC separations are compared to elucidate the elution characteristics of the block copolymer species.

Inconvertible p-tert-butylthiacalix[4]arene-core-star-shaped polystyrene conformers were synthesized by atom transfer radical polymerization (ATRP) using initiators of different conformations from p-tert-butylthiacalix[4]arene. 1H NMR and selective 1D NOESY analyses confirmed that the spatial structures of the initiator cores in the 4-arm star polymers were preserved during the polymerization process. While size exclusion chromatography (SEC) analyses revealed a diminishing difference in the hydrodynamic volume of the star polymer conformers as the molar mass increases, reversed phase liquid chromatography distinguishes the 4-arm star polymer having a cone-shaped core from the polymer having a 1,3-alternate-shaped core likely due to their isomeric locations of the hydrophobic tBu groups of the core. This result demonstrates that the inconvertible conformational structures of star polymers having the same composition exhibit distinguishable properties.

We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring Z1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring Z1.6±0.3) and the simulations (η0,linear/η0,ring Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem.

Detailed molecular characterization and fractionation were carried out for a polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) diblock copolymer prepared by linking PS-alkyne and PMMA-azide through a click reaction. PS and PMMA block precursors were prepared by atom transfer radical polymerization and anionic polymerization, and end-functionalized to have alkyne and azide group, respectively. As-synthesized block copolymer was characterized by solvent gradient reversed-phase liquid chromatography (RPLC) with multiple-detection for both separation and identification of byproducts. As-synthesized PS-b-PMMA contains various byproducts including unreacted precursor homo-polymers as well as byproducts formed during the synthesis of precursor polymers. To fractionate pure PS-b-PMMA out, two-step HPLC fractionation was employed. In the first step, PMMA homo-polymer was removed from the as-synthesized polymer using a C18 bonded silica column. In the second step, PS homo-polymer was removed to obtain pure PS-b-PMMA using a bare silica column. In both steps, multiple-injection method was used to facilitate the large scale fractionation procedure. A two-dimensional liquid chromatography method, solvent gradient RPLC for the first dimension and SEC for the second dimension was also conducted to map the molecular characteristics of the block copolymer and its byproducts.

We report on a novel synthetic route to synthesize relatively large quantities of polystyrene (PS) star polymers with targeted arm functionality and molar mass and their theological properties in the molten state. The synthetic route involves grafting styrene monomers onto a modified (aliphatic, alternating) polyketone backbone with a specific number of initiating grafting sites using controlled atom transfer radical polymerization (ATRP). Several polyketone precursors were used. This resulted in a large array of star polystyrenes with nonspherical cores and varying average arm length and number of arms. Their linear viscoelasticity was investigated and discussed in the context of the known response of anionically synthesized stars. Using a powerful characterization toolbox, including state-of-the-art interaction chromatography, rheometry, and tube modeling via the branch-on-branch (BoB) algorithm, we have assessed the viscoelasticity of these star polymers quantitatively. In particular, we have demonstrated a variability in molecular structure, which differs substantially from their anionically synthesized counterparts. Hence, whereas this new family of star polymers is not recommended for fundamental studies of polymer physics such as the molecular origin of relaxation mechanisms without prior extensive fractionation, they could be used in studies of mixtures as well as industrially relevant processing operations that require large amounts of polymeric stars.

The chemical homogeneity of telechelic polyisobutylene diol (PIB-diol), prepared by hydroboration-oxidation of allyl telechelic PIB obtained by reacting living PIB with allyltrimethylsilane, was investigated by liquid chromatography at critical conditions (LCCC) and HPLC coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). A normal phase gradient HPLC method was developed that was able to separate the as-synthesized PIB-diol into three components; PIB-diol, PIB-monool and PIB without any OH functionality. These were analyzed by MALDI-TOF MS, which suggested that the reaction of living PIB with allyltrimethylsilane was incomplete. LCCC using refractive index (RI) detector as a concentration detector allowed separation and quantification of PIB species according to their chemical heterogeneity (PIB-diol=95.3%, PIB-monool=3.3%, non-functional PIB=1.4%). The calculated number average functionality (Fn) of PIB-diol=1.94 suggests high quality of PIB-diol suitable for high molecular weight polyurethane synthesis.

This document defines terms relating to the properties of individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers. In the section on polymer solutions and amorphous bulk polymers, general and thermodynamic terms, dilute solutions, phase behaviour, transport properties, scattering methods, and separation methods are considered. The recommendations are a revision and expansion of the IUPAC terminology published in 1989 dealing with individual macromolecules, macromolecular assemblies, and dilute polymer solutions. New terms covering the principal theoretical and experimental developments that have occurred over the intervening years have been introduced. Polyelectrolytes are not included.

The epitaxial relationship in the thermal phase transition between double gyroid (DG) and hexagonally packed cylinder (HEX) phases in polystyrene-block-polyisoprene thin films on Si wafer was investigated using transmission electron microtomography and grazing incidence small-angle X-ray scattering. Two different types of epitaxial transitions were observed, and they appeared to be selectively favored depending on the transition direction. One type of epitaxial relationship prevails in the phase transition from DG to HEX upon heating in which {121}DG, {111}DG, and {220}DG are converted to {100}HEX, {110}HEX, and {001}HEX, respectively. The interphase planes are {220}DG and {001}HEX, and the cylinders meet the {220}DG plane perpendicularly (head-on, Type A) at the grain boundary between DG and HEX. Although there are small dimensional mismatch and distortion in the location of the cylinders in this epitaxial relationship, all cylinders are formed along the topologically equivalent DG skeletal path. On the ...

Partially sulfonated polystyrene-b-poly(dimethylsiloxane) (sPS-b-PDMS) block copolymer membranes were prepared using three different polymers with various molecular weights and block ratios. Eleven different products were obtained with controlled degree of sulfonation (DS) of PS block ranging from 22% to 48%, and they were cast into proton exchange membranes (PEMs). Each PEM was rigorously characterized to see the effect of molecular weight and PS content to PEM for direct methanol fuel cells (DMFC). The first set of sPS-b-PDMS with the highest molecular weight and 50% PS block ratio generally showed high mechanical strength and selectivity (proton conductivity/ methanol permeability), and the second set with medium molecular weight and 60% PS ratio showed high proton conductivity. The last PEM with the lowest molecular weight and 80% PS ratio exhibited a poor tensile strength which is not suitable for PEM application. When the membrane/electrode assemblies (MEAs) were fabricated using the sPS-b-PDMS PEMs with moderately high DS (~40%), one from the second set (moderate molecular weight, 60% PS content) showed the best power performance (90 mW/cm2 at 70 °C) in active mode DMFC operation, which was found to be 20% higher than that of Nafion 115 MEA.