We proposed an approach to precisely control the density of tethered chains on solid substrates using PEO-b-PS and PLLA-b-PS. As the crystallization temperature Tx increased, the PEO or PLLA lamellar crystal thickness d(L) increased as well as the reduced tethering density sigma; of the PS chains. The onset of tethered PS chains overcrowding in solution occurs at sigma(*) approximately 3.7-3.8 as evidenced by an abrupt change in the slope between (d(L))(-1) and Tx. This results from the extra surface free energy created by the tethered chain that starts to affect the growth barrier of the crystalline blocks.

A series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers were designed and synthesized to study the change in crystal orientation of PEO blocks under different confinement sizes. The volume fraction of PEO blocks (f PEO) in these copolymers was kept almost identical (the f PEO values were between 0.45 and 0.48) but with different number-average molecular weights for the PS and PEO blocks (M̄ n PEO and M̄ n PS). Therefore, the phase morphology of these copolymers was a lamellar structure with different PEO and PS layer thicknesses (d PEO and d PS) detected by synchrotron small-angle X-ray scattering (SAXS) experiments. Since the melting temperature of these PEO crystals is lower than the glass transition temperature of the PS layers, the PEO block crystals could be melted and recrystallized under one-dimensional (1D) confinement at different crystallization temperatures (T c). The PEO block crystal orientation changes were monitored using synchrotron wide-angle X-ray diffraction (WAXD) experiments. It was found that the crystalline PEO chain orientation (the c-axis in the crystals) underwent a change from being perpendicular (homogeneous) to the layer normal direction (n̂) at low T cs to parallel (homeotropic) at high T cs in these 1D confined samples with the d PEO ranging from 8.8 to 23.3 nm. However, with the gradual release of this 1D confinement, i.e., increasing the d PEO, a broad T c region in which the inclined c-axis orientation was originally observed in the PEO-b-PS with the low M̄ n PEO (8.7K g/mol) and M̄ n PS (9.2K g/mol) became increasingly narrowed by pushing the starting T c where the tilting initiates toward higher T c and reducing the ending T c where the parallel orientation of the c-axis with n̂ starts. In the PEO-b-PS sample with the highest M̄ n PEO (57K g/mol) and M̄ n PS (61.3K g/mol) in this study, this T c region was narrowed to less than 5 °C, suggesting the confinement size effect on the crystal orientation of the PEO crystals. The homogeneous to homeotropic orientation change of the c-axis in the PEO crystals with increasing T c was explained to be largely governed by the primary nucleation and crystal growth processes of the PEO blocks for developing the maximum crystallinity. A semiquantitative calculation was attempted to illustrate why the homogeneous orientation of the PEO crystals takes place in the 1D confinement based on the SAXS, WAXD, and differential scanning calorimetric results. It was expected that when the d PEO becomes large enough, the homogeneous orientation of the c-axis in the PEO crystals would disappear.

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A poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymer with number-average molecular weights of 7.7k g/mol for the PS block and 21.4k g/mol for the PEO block was used to study the PEO crystal orientation changes at different crystallization temperatures (T x ) via small-and wide-angle X-ray scattering techniques. For this diblock copolymer, an inverse hexagonal cylinder (IHC) phase morphology was identified with PS cylinders hexagonally packed within the PEO matrix. In this IHC morphology, the PEO blocks were tethered on the convex interfaces of the PS domains, and the crystallization of PEO blocks was outside of the cylinders. The crystal orientation of the PEO blocks (the c-axis of the PEO crystals) after crystallization among the PS cylinders was, for the first time, found to change with respect to the long cylinder axis, â, depending solely on T x . At very low T x 's, when the samples were quenched into liquid nitrogen, the crystals possessed a random orientation. When -30°C e T x e 5°C, PEO crystals had an orientation with their c-axis parallel to â. Within the temperature region of 10°C e T x e 20°C, the c-axis crystal orientation changed to be tilted with respect to â (the tilting angle was defined to be between the c-axis of the PEO crystals and â). This tilting angle increased with increasing T x . Finally, a major crystal orientation with the c-axes of PEO crystals perpendicular to â was observed when T x reached 30°C. Furthermore, it was particularly interesting that the PEO crystals in the IHC phase were oriented in two dimensions when T x ) 30°C. Namely, the PEO crystal growth was specifically grown along the {101 h0} planes of the hexagonal PS cylinders. The crystallite sizes were estimated by the Scherrer equation. The PEO crystal sizes, at least along one dimension, were on the scale of the sizes limited by the distance between the neighboring glassy PS cylinders in the hexagonal lattice.

Raman spectroscopy is a spectroscopic analysis technique that enables rapid qualitative and quantitative detection based on inelastic collision and Raman scattering intensity. This review detailed the generation principle, instrument composition, influencing factors, and common classifications of Raman spectrum. Furthermore, it summarized and forecast the research progress of Raman spectroscopy in the field of drug analysis simultaneously over the past decade, including the identification of active pharmaceutical ingredients (APIs), qualitative and quantitative studies of pharmaceutical preparations, detection of illicit drugs, the identification of Chinese herbal medicines, and the combination with other technologies. The development of Raman spectroscopy in other fields is additionally summarized.

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