Molecular Order of Topologically Variant Flexible Mesogens by 13C Nuclear Magnetic Resonance

Molecular Conformations of Shape Anisometrically Variant Mesogens in Liquid Crystalline Phase Studied by 13 C NMR Spectroscopy

Mesogens that vary in shape anisometry have been investigated by 13 C solid-state NMR in the liquid crystalline phase to inspect the conformations. The molecules examined comprise of (i) rod-like mesogen with three-phenyl ring core and terminal hexyloxy chains, (ii) three-ring core linked to the fourth phenyl ring via a spacer, and (iii) trimesic acid connected to three side arms core units through a spacer. The order parameter (Szz ) values for the phenyl rings of the rod-like mesogen are 0.65-0.68, while the mesogen with a three-ring core linked to a phenyl ring via spacer showed dissimilarity. Consequently, for the core unit phenyl rings, Szz is ~0.70, and the terminal phenyl ring showed a low value of 0.12. For the trimesic acid based mesogen, the Szz value for the side arm phenyl rings is ~0.53, and for the central phenyl ring, a very low value of 0.11 is witnessed. By considering the ordering of the rod-like mesogen as a yardstick and employing the ratios of Szz values of the phenyl rings, the average conformations of other mesogens are arrived. Accordingly, for the trimesic acid based mesogen, a tripod-like conformation instead of λ shape is proposed in the liquid crystalline phase.

Direct method to grasp molecular topology of mesogens through 13C-1H dipolar couplings

A prime factor in determining liquid crystalline phase formation is the overall molecular shape since molecules undergo rotational motion about the long axis. Molecular topology deals with the connectivity of atomic centers in a given molecular architecture, ultimately giving rise to the gross molecular shape. ¹³C NMR has emerged as the most important technique in establishing the molecular topology of mesogens in the liquid crystalline phase. In this work, we demonstrate the utility of ¹³C-¹H dipolar couplings determined from 2D separated local field NMR for finding the topology of three different mesogens in the liquid crystalline phase. The core unit of the investigated mesogens fundamentally differs, which may be categorized as rod-like, laterally substituted, and bent-core shapes. 1D and 2D ¹³C NMR measurements in the liquid crystalline phase revealed fascinating information. The ¹³C-¹H dipolar couplings extracted from 2D NMR are found to be sensitive to topologically variant core units. This permitted us to establish the molecular topology just by looking at the ¹³C-¹H dipolar couplings of the protonated carbons of the constituent phenyl rings. By considering the dipolar couplings of rod-like mesogens as a reference, the large variation in the magnitude of ¹³C-¹H dipolar couplings of the laterally substituted and bent-core mesogens is attributed to changes in the topology of their core units. The order parameters estimated from ¹³C-¹H dipolar couplings enabled visualization of the ordering array of phenyl rings of the mesogens. Interestingly large ¹³C-¹H dipolar couplings are observed for mesogens in which (a) laterally located phenyl ring and (b) central phenyl ring of bent-core mesogens exhibited different trends as revealed by the orientational order parameters.

Observation and Nursing of Adverse Reactions in Severe Patients with Enhanced MRI

In order to explore the observation and nursing of adverse reactions in severe patients with enhanced magnetic resonance imaging, a family nursing service model was proposed in patients with enhanced magnetic resonance imaging. 150 patients who underwent enhanced magnetic resonance imaging in a hospital were selected as the research objects. The patients were divided into two groups by random number table method. 75 patients in the control group received routine nursing intervention and 75 patients in the observation group received family nursing service intervention. The anxiety score, depression score, examination time, one-time success rate, comfort score, incidence of adverse reactions, excellent image quality rate and nursing satisfaction were compared between the two groups. The results showed that the anxiety score and depression score of the observation group were lower than those of the control group (P < 0.05), the examination time of the observation group was significantly shorter than that of the control group (P < 0.05), and the comfort score and one-time success rate of the observation group were significantly higher than those of the control group (P < 0.05). The incidence of adverse reactions was significantly lower than that in the control group (P < 0.05), the excellent and good image quality rate (95.00%) and nursing satisfaction (97.22%) were significantly higher than those in the control group (83.00%, 86.56%). This shows that the application effect of family nursing service mode in magnetic resonance enhanced scanning is remarkable. Therefore, the use of family care mode in MRI patient examination can effectively reduce patients' anxiety and depression scores, shorten examination time, reduce adverse reactions, improve the success rate of one-time examination, improve patients' comfort during examination and patients' evaluation of nursing services. The effect is ideal and worthy of clinical research and promotion.