Functionalized star-shaped polymers having PEO and/or polyglycidyl arms and their properties

The introduction of methacrylic, carboxylic and phosphate functional groups on the core and at the end of the poly(ethylene oxide) (PEO) arms in the PEO star-shaped polymers is described. In the polyglycidol (PGL) star-shaped polymers phosphate groups were attached to the PGL arms as side groups. Polymers were characterized by NMR and SEC analysis with triple detection. The conversion of the unsubstituted star-shaped polymers into functionalized has been confirmed by ¹H and ¹³C NMR spectra. The influence of the length of arms, their structure and the presence of functional groups on melting (T_m) and crystallization (T_c) temperatures and the degree of crystallinity (X_c) by differential scanning calorimetry (DSC) has been studied.     

Theory of chromatography of linear and cyclic polymers with functional groups

We discuss the chromatographic behavior of linear polymers and rings having specific (functional) adsorption-active groups. Functionalized eight-shaped, daisy-like and theta-shaped macromolecules are considered as well. By using a model of an ideal chain with point-type defects in a slit-like pore we derive equations for the distribution coefficient covering all modes of chromatography of functionalized polymers of any molar mass in both narrow and wide pores. Additionally simple approximate formulae are obtained for a number of important modes of chromatography; chromatograms are simulated for model mixtures of polydisperse non-functional and functional polymers. By using the theory we analyze separation of polymers by molar mass, functionality and topology. Although there is a principal possibility to use adsorption chromatography or size-exclusion chromatography (SEC), we conclude that the liquid chromatography at the critical condition (LCCC) is especially efficient for separation of polydisperse polymers by both functionality and topology. The theory predicts that functionalized linear and cyclic polymers can be separated from each others by LCCC even better than non-functionalized ones. The LCCC behavior of some other types of polymers such as comb-like and semicyclic ones is discussed as well.     

Topological separation of linear and star-shaped polystyrenes by off-line 2D chromatography. Stars having high molar mass arms and quantification of the star fraction

Off-line 2D separations on mixtures of linear and star-shaped polymers were performed using temperature gradient interaction chromatography (TGIC) as a first and SEC as a second dimension. The experiments resulted in clear separations of the linear and star shaped-structures for arm molar masses up to 42,000 g/mol. The resolution is nearly independent of the molar masses of the arms and depends only on the number of star arms. From the 2D chromatograms it is possible to determine the molar mass of the first branched structure, i.e. the three arm star. The evaluation of the relative peak volume allows a reliable estimation of the amount of branched structures in the complex mixture.     

Simplified theory for linear rheology of monodisperse linear polymers

A new version of the tube theory based on the de Gennes–Doi–Edwards reptation concept (reported in Likhtman and McLeish's work published in 2002) is evaluated, modified to allow for simplified computations, and used to study the relationship between zero‐shear viscosity and molecular weight for monodisperse entangled linear homopolymers. The Likhtman–McLeish model combines self‐consistent theories for contour length fluctuations and constraint release with reptation theory for monodisperse linear polymers. Because of the nature of the Rubinstein and Colby approach used for the treatment of constraint release, the related term is probabilistic and requires stochastic simulations for the calculation of the relaxation modulus G(t). This makes the Likhtman–McLeish model computationally difficult to use. In this work we solve this problem by generating an approximate closed‐form solution for the stochastic term. Then analytical integration of the relaxation modulus function G(t) provides an expression for the zero‐shear viscosity (η₀). Results of the computations of the zero‐shear viscosity and of the slope of η₀ versus molecular weight are compared with available experimental data for monodisperse entangled linear polystyrene and polyethylene (hydrogenated polybutadiene). The model is a major improvement over previous theoretical models, even if there is still some disagreement between the predictions and experimental data of the slope of η₀ versus molecular weight. The possibility of inferring monomer chemistry–dependent parameters from the zero‐shear viscosity remains a difficult task because of the introduction of a constraint‐release parameter. Nevertheless, the model is a useful tool for the prediction of linear viscoelasticity data. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 569–586, 2004     

线形和星形聚L-丙交酯大分子单体的合成

以辛酸亚锡为催化剂,分别以聚乙二醇、甲基丙烯酸羟乙酯、三羟甲基丙烷、季戊四醇、甘露醇和山梨醇等和L-丙交酯反应,得到末端为羟基的线形和星形聚L-丙交酯。通过和甲基丙烯酰氯反应,在上述线形和星形聚L-丙交酯成功引入双键,得到了相应的反应性大分子单体,其双键的存在经红外谱图和高锰酸钾试验得到证实。通过在过氧化二苯甲酰引发下的热交联,研究了上述大分子单体的反应性,发现端基数对交联产物的性质有一定影响。溶解试验、凝胶含量测定和热重分析表明,端基数目较多的大分子单体的交联产物有较高的凝胶含量,交联密度较大,热性能较好。     

Separation of parent homopolymers from diblock copolymers by liquid chromatography under limiting conditions of desorption 3. Role of column packing

The novel separation method, liquid chromatography under limiting conditions of desorption, LC LCD enables rapid one-step discrimination of both parent homopolymers from diblock copolymers. The low-molecular admixtures/impurities can be base-line separated, as well. The general rules for selection of the LC LCD columns are reviewed. Bare silica gel column packings are discussed in detail. Selected examples of separation are presented. They demonstrate that the principle of LC LCD separation is not affected by the particle size and initial purity of bare silica gel column packing nor by its effective pore diameter and volume. However, appropriate choice of the packing pore size facilitates base-line separation of particular sample constituents. Important may be the column history; columns saturated with previously adsorbed polymers may lose their performance. Up to a certain limit, success of the LC LCD separation does not depend on the column efficiency and reasonable results can be obtained even with the columns packed with rather big particles. This indicates possibility of the large-scale preparative applications and feasibility of the high-speed LC LCD separations.     

Numerical approximation of nonlinear and non-equilibrium two-dimensional model of chromatography

This article is concerned with the numerical approximation of a nonlinear model describing the two-dimensional non-equilibrium transport of multi-component mixtures in a chromatographic column of cylindrical geometry. In contrast to previous studies, the work includes joint analysis of deviations from equilibrium and the possibility that radial concentration profiles can develop. The considered radial gradients are typically ignored, which can be problematic in the case of non perfect injections. The model consists of nonlinear convection-diffusion partial differential equations coupled with some differential and algebraic equations. A high resolution finite volume scheme is applied to solve the model equations numerically. The considered case studies include single-component, two-component and three-component elution on fixed (non-movable) beds of liquid chromatography. The developed numerical algorithm is an efficient tool to study the effects of mass transfer kinetics on the elution profiles.     

Application of stimuli responsive polymers for sustainable ion exchange chromatography

Ion exchange processes are widely used in the food, bioprocessing and related industries for the isolation of proteins and other ionic species. Traditional ion exchange resins require salts, acids or bases for releasing adsorbed molecules creating a strong saline waste stream with negative environmental and economic impact. Stimuli responsive polymers (SRPs) with ion exchange functional groups can be used to selectively capture and release charged molecules from a complex mixture using physical stimuli to trigger conformational transitions in the polymer. The structural change of the polymers in response to a stimulus may lead to reduced ligand–target molecule interaction resulting in the release of the captured molecule without the use of chemical reagents, thereby reducing the environmental burden associated with ion exchange processes. The use of temperature responsive polymers has already been demonstrated for such applications at analytical scale. However, little progress has been made to extend these discoveries to the development of materials and methods amenable to industrial scale processing. So far, other SRPs such as, electric, magnetic and light responsive polymers remain largely unexplored for such application. This article discusses the potential of temperature responsive and other SRPs for developing sustainable ion exchange processes. It also highlights the material science and engineering challenges that need to be overcome to bring such processes to industrial application.     

Preparation of star polymers based on polystyrene or poly(styrene-b-N-isopropyl acrylamide) and divinylbenzene via reversible addition-fragmentation chain transfer polymerization

Star polymers based on styrene/divinyl benzene (St/DVB) and PSt-b-poly(N-isopropyl acrylamide) (NIPAAM)/DVB have been successively prepared by ‘arm-first’ method via reversible addition-fragmentation chain transfer (RAFT) polymerization. The linear macro RAFT agent PSt-SC(S)Ph was prepared by RAFT polymerization of St using benzyl dithiobenzoate and AIBN as RAFT agent and initiator. Successive RAFT polymerization of NIPAAM with PSt-SC(S)Ph as macro RAFT agent to afford diblock copolymer, PSt-b-PNIPAAM-SC(S)Ph. The coupling reactions of PSt-SC(S)Ph or PSt-b-PNIPAAM-SC(S)Ph in the presence of DVB produced the star copolymers, C(PSt)_n or C(PSt-b-PNIPAAM)_n. The molar ratio of DVB/PSt-SC(S)Ph and polymerization time influenced the yields, molecular weight and distribution of the star-shaped polymers, which was characterized by ¹H NMR and IR spectra, GPC measurements as well as DLS.     

Study on the mechanism of hindered sedimentation by ‘unified theory on solid-liquid separation’

The entire procedure of hindered sedimentation has been calculated by the introduction of new boundary conditions to the ‘unified theory on solid-liquid separation.’ During this study, the hindered sedimentation was defined as ‘a process of sedimentation with transmission of the gravitational force between the particles due to contact.’ The lower concentration limit, on which the ‘unified theory on solid-liquid separation’ is based, could not be applied. To understand the mechanism of hindered sedimentation, variations in the porosity during sedimentation were calculated by using our theory.     

有机多孔聚合物CO2捕集及分离性能的研究进展

有机多孔聚合物（porous organic polymers,POPs）是一类由有机构建单元连接而形成的新型多孔材料。由于其优异的物理化学稳定性以及CO₂吸附能力,近年来有关POPs在CO₂捕集和分离的研究成为一大研究热点。大量具有优异孔性质（比表面积和孔容）的POPs通过不同有机合成反应被成功地开发出来应用于CO₂吸附分离过程。本文介绍了POPs材料的CO₂捕集与分离性能的研究现状,总结了提高POPs材料CO₂分离性能的合成策略,重点分析了可以通过功能化增强吸附剂与二氧化碳分子之间的相互作用,来提高材料的CO₂分离能力的方法。     

Comparison of the surface energetics data of eucalypt fibers and some polymers obtained by contact angle and inverse gas chromatography methods

This study compares two approaches to determine the surface energy of solids, and its acid-base components in particular: inverse gas chromatography (IGC) and analysis of contact angle data using the Good-van Oss theory. The comparison is made in the context of wood fibers from Eucalyptus globulus and Eucalyptus regnans pulped by the kraft and neutral sulfite semi-chemical (NSSC) processes, and of selected polymers. Contact angles on wood fibers were measured using the Wilhelmy method and on polymer samples using the sessile drop technique. For the dispersive component of the surface energy, the level of agreement between the two approaches was reasonable, using alkanes for the IGC measurements and diiodomethane for the Wilhelmy and sessile drop techniques. However, agreement was poor for the acid and base characteristics when monopolar probes were used for IGC and water, formamide, and diiodomethane for contact angle measurements. The Good-van Oss approach suggested that all fibers and polymers are monopolarly basic, whereas IGC measurements suggested that they are bipolar. When new values were used for the acid and base components of the surface energy of the liquid probes based on the values for water proposed by Della Volpe and Siboni, all samples still appeared strongly basic. This is inconsistent with the chemical nature of the lignocellulosic fibers. Thus, the Good-van Oss approach provides a poor indication of acid-base properties of the surfaces of solids in suggesting that lignocellulosic fibers and polymers are strongly basic. The above issues as well as potential problems in measuring the surface energy of lignocellulosic fibers using the three-liquid procedure and the Good-van Oss approach are discussed.     

Fast determination of critical eluent composition for polymers by gradient chromatography

Gradient chromatography was applied in order to calculate the composition at elution for different methacrylates on normal phase columns. In addition the composition at elution was determined for polyethyleneoxide on a reverse phase column. It is shown that high molar mass polymers elute for a given homopolymer irrespective of their molar mass at the same eluent composition, which varies only slightly with gradient slope. In general the composition at elution in gradient chromatography is expected to be slightly lower than the true critical composition. For high molar mass polymers we found this composition to be close to the critical composition determined by isocratic experiments. The difference between the composition at elution and the true critical composition for a variety of polymethacrylates and for polyethyleneglycol was found to be only between 0.2 and 5%. Thus, after estimating the composition at elution, only a small number of additional isocratic experiments is needed to find the exact critical composition.     

Characterization of star-shaped poly(l-lactide)s by liquid chromatography at critical conditions

A series of linear and star-shaped poly(l-lactide)s (PLA's) have been prepared by living polymerization of l,l-dilactide (LA) and analyzed by liquid chromatography at critical conditions (LC-CC). For the analysis of the PLA's LC-CC conditions have been used corresponding to silica gel as the stationary phase and a mixture of 1,4-dioxane/n-hexane (56.25/43.75 by vol%) at 50 °C as the mobile phase. At the critical point of adsorption, a series of linear C₄H₉-PLA-OH's having molar masses (M_n) in the range from 2.3×10³ to 7.4×10⁴, prepared by ring-opening polymerization of LA initiated with Sn(OC₄H₉)₂ (THF, 80 °C), showed no dependence of the elution volumes on molar mass. In subsequent experiments, star-shaped PLA's bearing various numbers of PLA-OH arms (R-(PLA-OH)_x) have been prepared in a controlled synthesis starting from various polyols (R-(OH)_x) containing exclusively primary hydroxyl groups: diethyleneglycol (x=2), trimethylolpropane (x=3), di(trimethylolpropane) (x=4), dipentaerithritol (x=6), and poly(3-ethyl-3-hydroxymethyloxetane) (〈x〉=13.4) and LA monomer. As coinitiator/catalyst tin(II) octoate (Sn(Oct)₂) has been used (bulk polymerization, 120 °C). ¹H NMR analysis of the resulting star-shaped polymers revealed that all OH-groups in the polyols started growth of the PLA chains. The series of star-shaped PLA's have been analyzed by LC-CC as well as by two-dimensional (2D) chromatography (i.e. LC-CC versus size exclusion chromatography (SEC)) with regard to possible structural imperfections. It has been shown, that the LC-CC elution volumes of the resulting R-(PLA-OH)_x increase with the number of PLA-OH arms, allowing discrimination of the individual R-(PLA-OH)_x's in their mixture. An exponential increase of the retention volume as a function of the number of arms has been found. Eventually, LC-CC measurements of the elution volumes carried out for acetylated star-shaped PLA's (R(PLA-OOCCH₃)_x) have shown that for the interactions of the R-(PLA-OH)_x macromolecules with the column packing the hydroxyl end-groups are mostly responsible.     

The use of soluble polymers to effect homogeneous catalyst separation and reuse

The use of soluble polymeric ligands for homogeneous catalysts separation is reviewed with emphasis on work from the author's laboratory. Examples discussed include polyethylene-bound catalysts, poly(alkene oxide)-bound catalysts, poly(N-isopropylacrylamide)-bound catalysts, fluorous polymer-bound catalysts and amphoteric polymer-bound catalysts. The utility of these systems is also discussed in the broader context of polymer-supported catalysis and the advantages and limitations of soluble polymeric ligands are discussed in this context.     

Rosin‐based molecularly imprinted polymers as the stationary phase in high‐performance liquid chromatography for selective separation of berberine hydrochloride

A novel method for the separation of berberine hydrochloride has been developed. Berberine hydrochloride molecularly imprinted polymers were prepared by suspension polymerization in the aqueous phase using berberine hydrochloride as the template, methyl acrylic acid as a functional monomer, and ethylene glycol maleic rosinate acrylate (which contains a phenanthrene ring skeleton) and ethylene glycol dimethacrylate as combinatorial crosslinkers. The imprinted polymers were successfully used as a selective stationary phase in high‐performance liquid chromatography. Separation performance of the chromatographic column was determined from the selectivity (evaluated by separation factor) and sorption selectivity (evaluated by imprinting factor) of the molecularly imprinted and non‐imprinted polymers towards the template. The optimum conditions to maximize separation and imprinting factors were investigated. Acetic acid–methanol solution (0.05% v/v) was selected as the optimum mobile phase, while 0.2 mL min^?1 was chosen as the optimized flow rate for selective separation of berberine hydrochloride. The highest imprinting and separation factors obtained were 1.924 and 18.52, respectively. Simultaneously, the chromatographic column backpressure was stable and showed good permeability. The chromatographic column was used to separate effectively template molecules from coptis root extract and other analogues. Such chromatographic columns with high selectivity can be used to selectively separate berberine hydrochloride from other compounds. © 2014 Society of Chemical Industry     

Adsorption of star polymers studied by a new numerical mean field theory

We present a systematic theoretical investigation of star-like polymers of various architectures near adsorbing surface, using a new numerical self-consistent mean field theory. The comparison of the experimentally reported adsorption profiles with the predictions of our method shows excellent agreement. The study of the structural properties of the formed brushes indicates that as the number of branches is increased the number of adsorbed polymers is significantly reduced. Mixtures of different kinds of star polymers show interesting behaviors as the more branched polymers try to develop in the outer region of brush. We also estimate the forces obtained when curved surfaces come close as a function of the distance between the surfaces.     

A new thermoset for separation of polystyrene and naphthalene in preparative chromatography

Many research groups in recent years have demonstrated the importance of obtaining new materials and reducing environmental impact. In this context, the chemical modification of cellulose and its derivatives has received much attention. This study synthesized cellulose acetate gel (CAMDIH) obtained through the modification of cellulose acetate (CA) with a degree of substitution of 2.5, by crosslinking reactions using 4,4′‐diphenylmethane diisocyanate in homogeneous medium. The formation of crosslinks were observed by the presence of Fourier transform infrared spectroscopy absorption bands at 3046 and 864 cm^?1, which correspond to the absorption of aromatic groups associated with the incorporation of 4,4′‐diphenylmethane diisocyanate in the CA structure. The potential applications of the gel as a stationary phase were tested using column chromatography in the fractionation and separation of standard solutions of polystyrene and naphthalene. The findings showed the effectiveness of the gel as a stationary state in the separation of mixture compounds. Furthermore, the study found that CAMDHI is an innovative material when considering its simple synthesis and the low costs involved in the process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46063.     

Cost-efficient modeling of distributed molar mass and topological variations in graft copolymer synthesis by upgrading the method of moments

Cost-efficient deterministic method of moments solvers, as widely used to calculate average characteristics of chemical processes driven by population variations (e.g., average chain lengths), can be a posteriori extended with approximated solutions delivering distributed properties (e.g., chain length distributions). However, these solutions are rarely verified, specifically for complex systems with many population members and strong coupling, as is the case for industrially relevant free-radical-induced grafting (FRIG) toward graft copolymer (GC) synthesis with monomer unit dependent reactions. FRIG, as studied in the present work with polybutadiene at low styrene conversions, is an important chemical process, for example, the production of compatibilizers and high-impact materials. Deterministic model validation is uniquely performed by benchmarking the low to medium molar mass (MM) results (29 topologies) in the log-molar mass distribution with detailed matrix-based kinetic Monte Carlo simulation output, inherently capable of mapping distributions. The GC product is identified to be a heterogeneous mixture in MM, chemical composition, and molecular topology at any styrene conversion. The molecular structural evolution during GC synthesis is further theoretically related to both one-dimensional size-exclusion chromatography (1D-SEC) and two-dimensional liquid chromatography (2D-LC) analysis. It is shown that conventional SEC—even in the absence of broadening—is insufficient for GC separation, mainly due to the unavoidable coelution of topologically different GC species. In any case, the parallel running of advanced modeling tools allows for detailed molecular interpretation.