一种新的标定体积排除色谱（SEC）的方法

基于体积排除色谱中测得的淋出体积和动态激光光散射中测得的平动扩散系数都直接依赖于高分子的流体力学体积这一事实，本文在理论上提出了一种把淋出体积分布和平动扩散系数分布二者结合起来标定体积排除色谱的新方法，并且在实验上通过对宽分布的聚苯乙烯标准样品的测试证实了该方法的可行性．     

Thermodynamic characterization of poly(2,2,3,3,3‐pentafluoropropyl methacrylate)

The thermodynamic characterization of a fluorinated methacrylic homopolymer was conducted by means of inverse gas chromatography (IGC), at infinite dilution. The homopolymer under study, poly(2,2,3,3,3‐pentafluoropropyl methacrylate) (PPFPMA), was synthesized via a free radical polymerization reaction and was characterized by the employment of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and size exclusion chromatography (SEC) techniques. The specific retention volume of 15 solvents, used as probes, was used for the assessment of the Flory–Huggins interaction parameter, the weight fraction activity coefficient, the molar heat, energy and entropy of sorption, the partial heat of mixing of the probes, as well as the solubility parameter of the polymer. The results demonstrate that PPFPMA is insoluble in most organic solvents even at increased temperatures, with the exception of solvents like 2‐Butanone. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1826–1833, 2010     

Bulk properties of dendronized polymers with tailored end‐groups emanating from the same backbone

Dendronized polymers with a methacrylate backbone bearing pendant aliphatic polyester dendrons based on 2,2‐bis(methylol)propionic acid have been investigated by rheological measurements, differential scanning calorimetry (DSC), size exclusion chromatography (SEC), and ¹H NMR self‐diffusion techniques. The change in material properties due to the attachment of larger dendrons and/or different end‐groups to a backbone of the same length is investigated. Dendronized polymers of the second to fourth generation with hydroxyl, acetonide, or hexadecyl end‐group functionalities have been studied. DSC revealed that the glass transition temperature of the amorphous polymers increases with increasing size of the dendrons, and that the ability for the hexadecyl functional polymers to crystallize decreases with increasing size of dendrons. ¹H NMR self‐diffusion and longitudinal relaxation data are consistent with an elongated rod‐like model of the polymers in solution. Larger dendrons lead to a larger rod diameter that approximately double when increasing the generation of dendronized polymer from two to four. Rheological measurements demonstrated that the complex viscosity at low frequency increased with dendron size. Independently of the functionality, the second and third generation samples initially showed a Newtonian plateau, followed by a shear thinning region at higher frequencies. The fourth generation samples only showed shear thinning over the whole frequency region. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4496–4504, 2005     

An efficient avenue to poly(styrene)‐block‐poly(ε‐caprolactone) polymers via switching from RAFT to hydroxyl functionality: Synthesis and characterization

The recently introduced procedure of quantitatively switching thiocarbonyl thio capped (RAFT) polymers into hydroxyl terminated species was employed to generate narrow polydispersity (PDI ≈ 1.2) sulfur‐free poly(styrene)‐block‐poly(ε‐caprolactone) polymers (26,000 ≤ M_n/g·mol^?1 < 45,000). The ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) was conducted under organocatalysis employing 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD). The obtained block copolymers were thoroughly analyzed via size exclusion chromatography (SEC), NMR, as well as liquid adsorption chromatography under critical conditions coupled to SEC (LACCC‐SEC) to evidence the block copolymer structure and the efficiency of the synthetic process. The current contribution demonstrates that the RAFT process can serve as a methodology for the generation of sulfur‐free block copolymers via an efficient end group switch. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Study of the self‐diffusion of poly(ethylene glycol)s in poly(vinyl alcohol) aqueous systems

We have measured the self‐diffusion coefficients of a series of oligo‐ and poly(ethylene glycol)s with molecular weights ranging from 150 to 10,000, in aqueous solutions and gels of poly(vinyl alcohol) (PVA), using the pulsed‐gradient spin‐echo NMR techniques. The PVA concentrations varied from 0 to 0.38 g/mL which ranged from dilute solutions to polymer gels. Effects of the diffusant size and polymer concentration on the self‐diffusion coefficients have been investigated. The temperature dependence of the self‐diffusion coefficients has also been studied for poly(ethylene glycol)s with molecular weights of 600 and 2,000. Several theoretical models based on different physical concepts are used to fit the experimental data. The suitability of these models in the interpretation of the self‐diffusion data is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2396–2403, 1999     

Velocity‐correlation analysis in polymer–solvent mixtures

The subject of this article is the combined interpretation of intradiffusion and mutual‐diffusion data for polymer–solvent mixtures in terms of integrals over velocity self‐correlation functions and velocity cross‐correlation functions. The combination of mutual‐diffusion, intradiffusion, and activity data allows the evaluation of velocity‐correlation coefficients (VCCs) and distinct‐diffusion coefficients in systems containing one monodisperse solute. This study is the first attempt to extend these approaches to polymers that are polydisperse solutes. Because of the polydispersity, this correlation analysis may become critical for polymers. Its application to polydisperse samples requires the reduction of intradiffusion and mutual‐diffusion coefficients to the same average. After such a reduction, the VCCs and distinct‐diffusion coefficients are evaluated for a homologous series of poly(ethylene glycol)s (PEGs). Attractive PEG–PEG interactions depend on the chain length and concentration of PEG. In this analysis, network formation in PEG–water systems appears to be a smooth process. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 43–51, 2002     

Effects of dextran polydispersity on red blood cell aggregation

B 512 F dextran fractions of different polydispersities were prepared by fractionnal precipitation and preparative elution chromatography. By combination of low angle laser light scattering (LALLS) and gel permeation chromatography (GPC), absolute average molecular weights (MWs) and molecular weight distribution functions (MWDs) were determined. Static and thermodynamical properties in terms of polymer dimensions and second virial coefficient of dilute solutions of dextran in water have been investigated. The results indicate that dextran macromolecules in water are rather compact and impenetrable coils. Measuring the disaggregation shear stress of dextran-induced red blood cell aggregates by laser light reflectometry, the macromolecular bridging energy was shown to depend upon dextran sample polydispersity. This reflects the weak and reversible character of red blood cell aggregation by dextran chains in physiological saline solution.     

Polymer characterization by interaction chromatography

Liquid chromatography (LC) is a powerful tool for the characterization of synthetic polymers, that are inherently heterogeneous in molecular weight, chain architecture, chemical composition, and microstructure. Of different versions of the LC methods, size exclusion chromatography (SEC) is most commonly used for the molecular weight distribution analysis. SEC separates the polymer molecules according to the size of a polymer chain, a well‐defined function of molecular weight for linear homopolymers. The same, however, cannot be said of nonlinear polymers or copolymers. Hence, SEC is ill suited for and inefficient in separating the molecules in terms of chemical heterogeneity, such as differences in chemical composition of copolymers, tacticity, and functionality. For these purposes, another chromatographic method called interaction chromatography (IC) is found as a better tool because its separation mechanism is sensitive to the chemical nature of the molecules. The IC separation utilizes the enthalpic interactions to vary adsorption or partition of solute molecules to the stationary phase. Thus, it is used to separate polymers in terms of their chemical composition distribution or functionality. Further, the IC method has been shown to give rise to much higher resolution over SEC in separating polymers by molecular weight. We present here our recent progress in polymer characterization with this method. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1591‐1607, 2005     

Application of free‐volume theory to self diffusion of solvents in polymers below the glass transition temperature: A review

Theories based on free‐volume concepts have been developed to characterize the self and mutual‐diffusion coefficients of low molecular weight penetrants in rubbery and glassy polymer‐solvent systems. These theories are applicable over wide ranges of temperature and concentration. The capability of free‐volume theory to describe solvent diffusion in glassy polymers is reviewed in this article. Two alternative free‐volume based approaches used to evaluate solvent self‐diffusion coefficients in glassy polymer‐solvent systems are compared in terms of their differences and applicability. The models can correlate/predict temperature and concentration dependencies of the solvent diffusion coefficient. With the appropriate accompanying thermodynamic factors they can be used to model concentration profiles in mutual diffusion processes that are Fickian such as drying of coatings. The free‐volume methodology has been found to be consistent with molecular dynamics simulations. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Size exclusion chromatography with Corona charged aerosol detector for the analysis of polyethylene glycol polymer

A technique of using size exclusion chromatography (SEC) with the Corona charged aerosol detector (CAD) was developed and evaluated in comparison with refractive index (RI) and evaporative light scattering detection (ELSD) for fast screening of polyethylene glycol (PEG), a polymer used in preparing pegylated pharmaceutical compounds. These detection techniques were used in the analysis of multiple lots of PEG reagents. CAD was found to provide more accurate impurity and polydispersity profiles of PEG reagents that better differentiate their quality, while RI was not suitable for this application due to its low sensitivity and ELSD led to underestimation of the impurity and polydispersity. The accuracy of polydispersity determination by SEC-CAD was validated against a commercial reference standard of known polydispersity. The SEC-CAD technique and the observed differences between the three detectors can also be applied to polymer analysis in general.     

Synthesis and characterization of 6‐ and 12‐arm star polymers by nitroxide‐mediated radical polymerization of St and MA from dendritic TIPNO‐based hexafunctional and dodecafunctional macroinitiators

Dendritic multifunctional macroinitiators having six and 12 TIPNO‐based alkoxyamines, TIPNO‐6 and TIPNO‐12 , were synthesized and used in the living radical polymerization of styrene (St), methyl acrylate (MA), N,N‐dimethylacrylamide (DMAAm), and isoprene (IP). The polymerizations of St initiated with TIPNO‐6 gave 6‐arm star polymers with narrow polydispersities of 1.14–1.18. In the polymerizations of MA initiated with TIPNO‐6 and TIPNO‐12 , the influences of added TIPNO on the polydispersity indexes (PDIs) of the resulting star polymers were first investigated, and this led to the successful formation of poly(MA) star polymers with narrow polydispersities (1.10–1.18). Moreover, the polymerizations of DMAAm and IP from TIPNO‐6 in the presence or absence of TIPNO were briefly investigated. The benzyl ether bonds of the poly(St) and poly(MA) star polymers were cleaved by treating with Me₃SiI or Pd/C, and the resulting arm's parts were analyzed with SEC. The PDIs of the resulting arm parts were low (1.19–1.23), and the M_ns agreed with the M_n,theor, indicating that the poly(St) and poly(MA) star polymers had well‐controlled arms. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4364–4376, 2007     

Molecular weight distribution formed during free‐radical polymerization in the presence of polyfunctional chain transfer agents

Free‐radical polymerization of styrene was carried out in the presence of chain transfer agents (CTAs) with functionality, f = 1–4. The size exclusion chromatography (SEC) with an ultraviolet absorption detector (UV) was used to measure the molecular weight distribution (MWD). A Monte Carlo simulation method proposed earlier was used to investigate the experimental results. In this simulation method, one can observe the structure of each polymer molecule directly, and very detailed information can be obtained in a straightforward manner, including the elution curve of SEC. It was found that up to the functionality f = 3, the equal reactivity model that assumes the reactivity of all functional groups in a CTA is equal agrees reasonably well with the experimental results. However, with f = 4, the reactivity of the fourth functional group seems to decrease and the substitution effects may need to be accounted for to fine control the formed branched structure. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1267–1275, 1999     

Differential size‐exclusion chromatography for the analysis of gelatin–polyelectrolyte complexes

Differential size‐exclusion chromatography (SEC) is used to characterize complexes formed between gelatin and two synthetic polyelectrolytes, sodium poly(styrenesulfonate) and sodium poly(2‐acrylamido‐2‐methylpropanesulfonate). The analysis is performed under aqueous, low‐salt conditions where maximum complexation between gelatin and the polyelectrolytes occurs. The adsorption effects that are commonly encountered in conventional SEC for gelatin and other charged polymers chromatographed under these solution conditions are minimized, because the columns are constantly equilibrated with the analytes in the mobile phase. Analyte solutions of identical composition, but of higher or lower concentration than that contained in the mobile phase, are injected, resulting in positive or negative detector responses, respectively. This method can separate the complexes from individual components, and can be used to determine relative sizes and stoichiometries of the complexes as a function of both the input ratio of gelatin to polyelectrolyte and the molecular weight of the polyelectrolyte. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 275–280, 1999     

Viscometric,light scattering,and size‐exclusion chromatography studies on the structural changes of aqueous poly(vinyl alcohol) induced by γ‐ray irradiation

The crosslinking processes of aqueous poly(vinyl alcohol) (PVA) by γ‐ray irradiation were studied by viscometry, dynamic and static light scattering (DLS and SLS), as well as size exclusion chromatography (SEC). Increases in the intrinsic viscosity ([η]), molecular weight (M_w), hydrodynamic radius (R_h), and radius of gyration (R_g), and a decrease in second virial coefficient (A₂) were observed after γ‐ray irradiation. However, both the values of [η] and A₂ for irradiated PVA fell below the data of unirradiated PVA solutions, suggesting a conformational change of PVA chains after γ‐ray irradiation. This structural change of PVA as a result of γ‐ray irradiation was also indicated by the decreases in R_g/R_h from 1.5 to 1.39 by SLS and DLS, and in Mark–Houwink exponent α_η from 0.54 to 0.26 by SEC‐Viscometry. The broadening of the M_w distribution (MWD) as indicated by the polydispersity index increased from 2.2 to 6.5 because of γ‐ray irradiation. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 214–221, 2000     

Revised insights into templating radical polymerization within nanoreactors

The field of polymer chemistry is currently experiencing major research efforts into development of novel techniques for synthesis of polymers with well‐controlled microstructure. Recently, a new method has been reported [McHale et al., Nat. Chem. 2012, 4, 491–497] whereby high molecular weight and low dispersity polymer can be obtained by a radical polymerization process via the use of solely physico‐chemical interactions. This work was based on the combination of H‐bonding templated polymerization confined within nanoreactors of self‐assembled block copolymers. Herein, this system is thoroughly investigated to fully elucidate the underlying mechanism. Modification of physico‐chemical parameters, kinetic parameters as well as observations of size exclusion chromatography (SEC) results and colloidal behavior in various solvents provide revised insights into the mechanism. Through detailed NMR and SEC investigations, it is demonstrated that the SEC secondary peak originally believed to be the high molecular weight “daughter” polymer actually corresponds to nanoparticles containing the daughter polymer. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1590–1600     

Phase equilibrium and diffusion of solvents in polybutadiene: A capillary‐column inverse gas chromatography study

The capillary‐column inverse gas chromatography method was used to measure the diffusion and partition coefficients of ethylbenzene, styrene, and acrylonitrile in polybutadiene (PBD) at infinite dilution of the solvents. Experiments were performed over a temperature range of 50–125 °C. At temperatures well above the glass‐transition temperature of PBD, the diffusivities were correlated using an Arrhenius expression. The Arrhenius parameters in turn were intercorrelated and shown to be a function of the occupied volume, thus providing a method for predicting the diffusion of other solvents in the same polymer. Further, the activation energy was predicted using the Duda‐Vrentas free‐volume approach. The activation energy thus obtained was compared with the activation energy of the Arrhenius approach. The weight‐fraction activity coefficient data were compared to the predictions of the group contribution, lattice‐fluid equation‐of‐state, and the UNIquac Functional‐group Activity Coefficient (UNIFAC) free‐volume models. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1046–1055, 2002     

Synthesis and characterization of tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers via RAFT polymerization

A new bipyridine‐functionalized dithioester was synthesized and further used as a RAFT agent in RAFT polymerization of styrene and N‐isopropylacrylamide. Kinetics analysis indicates that it is an efficient chain transfer agent for RAFT polymerization of the two monomers which produce polystyrene and poly(N‐isopropylacrylamide) polymers with predetermined molecular weights and low polydispersities in addition to the end functionality of bipyridine. The bipyridine end‐functionalized polymers were further used as macroligands for the preparation of star‐shaped metallopolymers. Hydrophobic polystyrene macroligand combined with hydrophiphilic poly(N‐isopropylacrylamide) was complexed with ruthenium ions to produce amphiphilic ruthenium‐cored star‐shaped metallopolymers. The structures of these synthesized metallopolymers were further elucidated by UV–vis, fluorescence, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC) as well as NMR techniques. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4225–4239, 2007     

Rapid determination of molecular parameters of synthetic polymers by precipitation/redissolution high‐performance liquid chromatography using “molded” monolithic column

Rapid high‐performance liquid chromatography (HPLC) of polystyrenes, poly(methyl methacrylates), poly(vinyl acetates), and polybutadienes using a monolithic 50 × 4.6 mm i.d. poly(styrene‐co‐divinylbenzene) column have been carried out. The separation process involves precipitation of the macromolecules on the macroporous monolithic column followed by progressive elution utilizing a gradient of the mobile phase. Depending on the character of the separated polymer, solvent gradients were composed of a poor solvent such as water, methanol, or hexane and increasing amounts of a good solvent such as THF or dichloromethane. Monolithic columns are ideally suited for this technique because convection through the large pores of the monolith enhances the mass transport of large polymer molecules and accelerates the separation process. Separation conditions including the selection of a specific pair of solvent and precipitant, flow rate, and gradient steepness were optimized for the rapid HPLC separations of various polymers that differed broadly in their molecular weights. Excellent separations were obtained demonstrating that the precipitation‐redissolution technique is a suitable alternative to size‐exclusion chromatography (SEC). The molecular weight parameters calculated from the HPLC data match well those obtained by SEC. However, compared to SEC, the determination of molecular parameters using gradient elution could be achieved at comparable flow rates in a much shorter period of time, typically in about 1 min. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2767–2778, 2000     

Synthesis and characterization of model polybutadiene‐1,4‐b‐polydimethylsiloxane‐b‐polybutadiene‐1,4 copolymers

Model copolymers of poly(butadiene) (PB) and poly(dimethylsiloxane) (PDMS), PB‐b‐PDMS‐b‐PB, were synthesized by sequential anionic polymerization (high vacuum techniques) of 1,3‐butadiene and hexamethylciclotrisiloxane (D₃) on sec‐BuLi followed by chlorosilane‐coupling chemistry. The synthesized copolymers were characterized by nuclear magnetic resonance (¹H NMR), size‐exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). SEC and ¹H NMR results showed low polydispersity indexes (M_w/M_n) and variable siloxane compositions, whereas DSC and TGA experiments indicated that the thermal stability of the triblock copolymers depends on the PDMS composition. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2726–2733, 2007     

Evolution of the termination rate coefficient in styrene polymerization

Styrene bulk polymerization was conducted at 70 °C with a high initiator concentration, and this ensured that the dominant chain‐stopping mechanism was the combination of free radicals. The evolution of the molecular weight distribution (MWD) of the polymer was measured via the periodic removal of samples during the course of the reaction and their analysis with gel permeation chromatography. The overall termination rate coefficient was independent of the conversion in the dilute regime, as observed from cumulative MWDs. In the middle of the conversion range, the observed trend was compatible with a translational‐diffusion‐controlled mechanism for the termination step. A bimodal distribution of the molecular weights was also found at high conversions and could be explained in terms of an increase in the free‐radical concentration and a very low termination rate coefficient. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 178–187, 2005