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Temperature gradient interaction chromatography (TGIC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) were applied for the characterization of highly branched polystyrenes (PS) prepared by linking living polystyryl anions using 4-chlorodimethylsilylstyrene. Reversed-phase (RP)-TGIC showed an unexpectedly high resolution according to the number of branches despite significant overlap of the molecular weight as confirmed by MALDI-TOF MS. The enhancement of the resolution is ascribed to the contribution of the nonpolar groups in the branched PS: the dimethylsilyl groups in the branching unit as well as the sec-butyl initiator groups. As the number of branches increases, the number of nonpolar groups increases, which in turn increases the RP-TGIC retention synergistically with increasing molecular weight. In contrast, a poorer resolution was found in normal-phase-TGIC, in which the nonpolar groups reduce the retention. The resolution in RP-TGIC appears superior to that of liquid chromatography at the chromatographic critical condition (LCCC) of PS. It is seemingly due to the synergistic contribution of the incremental PS molecular weight to the functionality in the branched PS in RP-TGIC while only the functionality contributes to the separation in LCCC. This type of resolution enhancement could be utilized efficiently for the analysis of highly branched polymers such as dendrimers or hyperbranched polymers.

Temperature gradient interaction chromatography (TGIC) was applied for the separation of stereoregular poly(ethyl methacrylate) (PEMA) according to the tacticity. The three PEMA samples with differing tacticity (rr triad content: 0, 53, and 91%) prepared by anionic polymerization were used. C18 bonded silica and a mixture of C[H.sub.2][Cl.sub.2] and C[H.sub.3]CN (30/70, v/v) were used as stationary and mobile phase, respectively. TGIC was able to separate the PEMA samples, showing the increasing retention in the order of decreasing rr triad contents; however TGIC elution peaks of the three PEMAs were not fully resolved but, rather, were partially overlapped. To isolate the tacticity effect from the molecular weight effect on the TGIC retention, the PEMA samples were fractionated by TGIC, and the accurate molecular weight of the fractions was determined by MALDI-TOF mass spectrometry. The fractions showed a much narrower molecular weight distribution than the mother PEMAs. The TGIC fractions of similar molecular weight but with different tacticity were fully resolved by TGIC, but mother PEMAs were not. These results indicate that the retention in TGIC is affected by both tacticity and molecular weight.