Fluorinated Polydopamine Shell Decorated Fillers in Polytetrafluoroethylene Composite for Achieving Highly Reduced Coefficient of Thermal Expansion.

The noticeable difference in the coefficient of thermal expansion (CTE) for polytetrafluoroethylene (PTFE) coatings and copper substrates is a major challenge for thermal debonding of the copper-clad laminate (CCL) in high-frequency communications. Theoretically, ceramic fillers with low CTEs in the coating can effectively reduce the gap, and there remains a trade-off between the dispersibility of fillers and the interfacial interactions with the polymeric matrix. Here, we propose a novel approach to prepare a pentafluorobenzoyl chloride (PFBC)-modified polydopamine (PDA) shell on silica particles by using amidation. Such modified particles perform excellent dispersion and exhibit diminished interfacial gaps in the PTFE matrix, which highly reduces CTE to 77 ppm/°C, accounting for only 48.1% of the neat coating. Moreover, the composite exhibits enhanced mechanical strength and toughness, and consequently suppresses thermal debonding in CCL under high-temperature conditions. Therefore, results present a promising potential for its use in the next-generation CCL of high-frequency communication devices.

PTFE Crystal Growth in Composites: A Phase-Field Model Simulation Study.

We investigated, via a phase-field model simulation, the effects of a matrix's properties and a filler's characters on the polytetrafluoroethylene (PTFE) crystal growth process in composites under various supercooling degrees. The results show that the supercooling degree has a deciding influence on the crystal growth process. The intrinsic properties of PTFE polymer, such as anisotropic strength and phase transition latent heat, affect the growth rate, orientation, and interfacial integrity of the crystal trunk and the branching of the PTFE crystal growth process. The factors of the PTFE crystallization process, such as anisotropic strength and phase translation interface thickness, affect the uniformity and crystallization degree of the PTFE crystal. In the composites, the biphasic interface induces the crystal growth direction via the polymer chain segment migration rate, of which the degree depends on the shapes of the filler and the PTFE crystal nucleus. According to the results, choosing the low molecular weight PTFE and mixture filler with various particle sizes and surface curvatures as the raw materials of PTFE-based composites improves the crystallization of the PTFE matrix.

Predictors for symptomatic intracranial hemorrhage after intravenous thrombolysis with acute ischemic stroke within 6 h in northern China: a multicenter, retrospective study.

BACKGROUND AND PURPOSE: This study assessed the predictive factors for symptomatic intracranial hemorrhage (sICH) in patients with acute ischemic stroke (AIS) after receiving intravenous thrombolysis (IVT) within 6 h in northern China. METHODS: We retrospectively analyzed ischemic stroke patients who were treated with IVT between November 2016 and December 2018 in 19 hospitals in Shandong Province, China. Potential predictors of sICH were investigated using univariate and multivariate analyses. RESULTS: Of the 1293 enrolled patients (845 men, aged 62 ± 11 years), 33 (2.6%) developed sICH. The patients with sICH had increased coronary heart disease (36.4% vs. 13.7%, P = 0.001), more severe stroke (mean National Institutes of Health Stroke Scale [NIHSS] score on admission of 14 vs.7, P < 0.001), longer door-to-needle time [DNT] (66 min vs. 50 min, P < 0.001), higher blood glucose on admission, higher white blood cell counts (9000/mm3 vs. 7950/mm3, P = 0.004) and higher neutrophils ratios (73.4% vs. 67.2%, P = 0.006) et al. According to the results of multivariate analysis, the frequency of sICH was independently associated with the NIHSS score (OR = 3.38; 95%CI [1.50-7.63]; P = 0.003), DNT (OR = 4.52; 95%CI [1.69-12.12]; P = 0.003), and white blood cell count (OR = 3.59; 95%CI [1.50-8.61]; P = 0.004). When these three predictive factors were aggregated, compared with participants without any factors, the multi-adjusted odds ratios (95% confidence intervals) of sICH for persons concurrently having one, two or three of these factors were 2.28 (0.25-20.74), 15.37 (1.96-120.90) and 29.05 (3.13-270.11), respectively (P for linear trend < 0.001), compared with participants without any factors. CONCLUSION: NIHSS scores higher than 10 on admission, a DNT > 50 min, and a white blood cell count ≥9000/mm3 were independent risk factors for sICH in Chinese patients within 6 h after IVT for AIS.