Adsorption and Desorption of Macromolecules on the Solid Surfaces Studied by On-Line SEC. 1. The Principle of Method

and, Dušan Berek; Nguyen, Son Hoai

doi:10.1021/ma970984l

Cited by 21 publications

(16 citation statements)

References 19 publications

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“…Recently, we have found that the attachment of macromolecules onto the surface of a nonporous adsorbent is very fast [13]. The pulling of macromolecules from the desorli zone into (narrow) packing pores in LC-LCA seems to be a very fast process.…”

Section: Resultsmentioning

confidence: 99%

Liquid chromatography under limiting conditions of adsorption and limiting conditions of desorption for separation of complex polymers. The role of “flower-like” interactions of macromolecules

Šnauko

Berek

2003

Chromatographia

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Liquid chromatography of polymers under limiting conditions (LC-LC) of enthalpic interactions employs different velocities of small (eluent or auxiliary liquid) molecules and large (sample) molecules within a HPLC column. Slowly moving small molecules of a liquid act as a "barrier" hindering fast progression of large molecules during with exclusion retention mechanism. Under specific ("limiting") conditions the low molar mass barrier enables a molar mass independent polymer elution. Depending on the applied barrier mechanism (adsorption, partition, phase separation) and on the experimental arrangement (eluent as a continuous barrier or narrow zone of auxiliary liquid as a local barrier) six different modes of LC-LC can be created. Here, we deal with the limiting conditions of adsorption (LC-LCA-eluent as a barrier) and the limiting conditions of desorption (LC-LCD -the barrier created by a zone of an auxiliary liquid), which utilize adsorption barrier mechanism.Reduced sample recovery was repeatedly observed in many LC-LCA systems, especiallywhen working with the narrow -pore column packing. The fraction of macromolecules retained within the LC-LCA column raised with the decreasing pore size of the column packing and with the increasing molar mass of the polymer samples. With the same both polymers and column packing, LC-LCD yielded full sample recovery. This finding is explained by the difference in the liquid layer composition on the outer surface of the packing particles and on the walls of broader pores compared to that within the narrow pores. Local equilibrium within the liquid phase seems not to be reached in the narrow packing pores. This means that adsorption promoting state is preserved within narrow pores of the LC-LCA column, which may lead to the "flower-like" adsorption of macromolecules. Polymer species penetrate ("reptate') into these narrow packing pores to be strongly adsorbed by a multiple attachment. The desorption of the flower-like adsorbed macromolecules is slow and, consequently irregularities of chromatographic bands and reduced sample recovery may appean In contrast, the desorption promoting state remains in the narrow pores of the LC-LCD packing and it prevents entrapment of macromolecules. The flower-like adsorption of macromolecules is not feasible in LC-LCD and this results in high sample recovery. Our results indicate an important advantage of the LC-LCD over the LC-LCA method and may also help explaining some irregularities observed in liquid chromatography under critical conditions of adsorption.

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Section: Resultsmentioning

confidence: 99%

Liquid chromatography under limiting conditions of adsorption and limiting conditions of desorption for separation of complex polymers. The role of “flower-like” interactions of macromolecules

Šnauko

Berek

2003

Chromatographia

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“…Off-line experiments are being carried out in a first step prior to testing an on-line coupled system, as already has been done by some other authors with different systems. [28,291 By adding a SEC column in series with the first LC LCA system, both composition and molecular size of copolymer will be quantified simultaneously. r271 Further improvements will be focused on enlarging the application window of LC LCA separation.…”

Section: Discussionmentioning

confidence: 99%

Determination of the Composition of Statistical Copolymers by Liquid Chromatography Under Limiting Conditions of Adsorption

Sauzedde

Hunkeler

2001

International Journal of Polymer Analysis and Characterization

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Liquid chromatography under limiting conditions of adsorption (LC LCA) was applied to determine the composition of statistical poly(styrene-methyl methacrylate) (PS/ MMA) copolymer standards. Two series of copolymers were prepared and characterized. The first series varies with respect to the styrene/methyl methacrylate ratio in the copolymer, at a constant molar mass (220,000 i 30,00Og/mol), while the second has molar masses from 20,000 to 250,000 g/mol at a molar styrene fraction of 0.5 f 0.02. The copolymers were fractionated using size exclusion chromatography (SEC) and LC LCA.In the case of LC LCA, two different ratios of THF to n-hexane were employed. Low and high LC LCA were differentiated according to the composition of the binary eluent, the lowest n-hexane content corresponding to low LC LCA. The influence of the molar mass on the peak distance, defined as the difference of retention volume between SEC and LC LCA, was negligible in the studied range compared to composition effect. A calibration curve was subsequently established and correlated the peak distance to the copolymer composition. The application range of the calibration curve was found to vary with the percentage of n-hexane contained in the eluent and corresponded to 0.1 -0.4 and 0.2-0.6 molar fraction of styrene for low and high LC LCA, respectively. Using these calibration curves, the P(S/MMA) copolymer composition distribution calculation was estimated for one sample. Therefore, the limiting condition method can be coupled on-line or off-line with SEC to perform a simultaneous characterization of the compositions and molar mass distributions.

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“…Based on the full absorption and adsorption theory,64–67 graft efficiency ( G e ) was determined using high performance liquid chromatography (SiO 2 , 100 Å, 5 µm) with isocratic elution, CHCl 3 /DMF = 3:7 v/v. Due to the different interactions between SAN chains or graft (or grafted) SAN chains and hydroxyl groups on the surface of SiO 2 particles in column, they can be separated and then quantified using a UV detector.…”

Section: Methodsmentioning

confidence: 99%

Graft Copolymerization of Styrene and Acrylonitrile in the Presence of Poly(propylene glycol): Kinetics and Modeling

et al. 2012

Macro Reaction Engineering

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A heterogeneous polymerization model, including an initial solution polymerization model and a later two‐phase polymerization model, is developed to describe graft free‐radical copolymerization of styrene and acrylonitrile in the presence of poly(propylene glycol). The diffusion‐controlled termination, initiation, propagation, and transfer in the dispersed phase are considered reasonably. The model describes the polymeriztion kinetics well. The main polymerization locus shifts from the continuous phase into the dispersed phase at monomer conversion of ≈0.03–0.05, leading to sharp increase in polymerization rate and molecular weight, decrease in graft efficiency and broadening of the MWD.

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Adsorption and Desorption of Macromolecules on the Solid Surfaces Studied by On-Line SEC. 1. The Principle of Method

Cited by 21 publications

References 19 publications

Liquid chromatography under limiting conditions of adsorption and limiting conditions of desorption for separation of complex polymers. The role of “flower-like” interactions of macromolecules

Liquid chromatography under limiting conditions of adsorption and limiting conditions of desorption for separation of complex polymers. The role of “flower-like” interactions of macromolecules

Determination of the Composition of Statistical Copolymers by Liquid Chromatography Under Limiting Conditions of Adsorption

Graft Copolymerization of Styrene and Acrylonitrile in the Presence of Poly(propylene glycol): Kinetics and Modeling

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