The effects of molecular weight distribution on the phase stability of polymer mixtures were explored theoretically and experimentally. Based on the lattice‐fluid theory and volume‐fluctuation thermodynamics, the spinodal conditions for a lattice‐fluid mixture of two polymers with molecular weight distribution were derived. The results indicated that the phase stability of a polymer mixture decreases by increasing the molecular weight distribution of polymers in the blend. To confirm the theoretical results with experiments, the changes in the spinodal temperatures of poly(ethyl methacrylate)/polystyrene (PEMA/PS) blends and tetramethyl polycarbonate/polystyrene (TMPC/PS) blends were examined when each component has a different molecular weight distribution. When the weight‐average molecular weight of each component is the same, a blend composed of polymers having broad molecular weight distribution always exhibited lower phase separation than that composed of polymers having narrow molecular weight distribution at the same blend composition. Copyright © 2004 Society of Chemical Industry
Tetramethylpolycarbonate-block-poly(styrene-co-acrylonitrile) (TMPC-block-SAN) block copolymers containing various amounts of acrylonitrile (AN) were examined as compatibilizers for blends of polycarbonate (PC) with poly(styrene-co-acrylonitrile) (SAN) copolymers. To explore the effects of block copolymers on the compatibility of PC/SAN blends, the average diameter of the dispersed particles in the blend was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fibre retraction technique and an asymmetric double-cantilever beam fracture test. Reduction in the average diameter of dispersed particles and effective improvement in the interfacial properties was observed by adding TMPC-block-SAN copolymers as compatibilizer of PC/SAN blend. TMPC-block-SAN copolymer was effective as a compatibilizer when the difference in the AN content of SAN copolymer and that of SAN block in TMPC-block-SAN copolymer was less than about 10 wt%.
Background The aim of this study to assess the efficacy and safety of adalimumab (ADA), a monoclonal antibody against tumour necrosis factor α (TNF-α), and to explore predictors of response in Korean patients with ulcerative colitis (UC). Methods We conducted a prospective observational multicenter study over 56 weeks in adult patients with moderately to severely active UC. Clinical response and remission were assessed by Mayo score. Mucosal healing was defined as Mayo subscore 0 or 1. Faecal calprotectin (FC) were assessed at baseline, week 8 and 56. Adalimumab drug levels were checked at week 8 and at loss of response. Missing or incomplete data were handled using the nonresponder imputation method. Results A total of 146 patients were enrolled and included in the analysis. Clinical response rates were 52.1% (76/146) and 37.7% (55/146) at week 8 and 56, respectively. Clinical remission was achieved in 24.0% (35/146) and 21.9% (32/146) of patients at week 8 and 56. Steroid-free remission rates were 21.2% (31/146) at week 56. Mucosal healing rates were 39.0% (57/146) and 30.1% (44/146) at week 8 and 56. Prior use of anti-TNF-α did not affect the clinical and endoscopic responses. Treatment persistence was achieved in 57.5% (84/146) of patients at week 56. Adalimumab drug level was significantly higher in patients with clinical response (10.8 vs. 8.0, p = 0.004), clinical remission (11.7 vs. 8.8, p = 0.007) and mucosal healing (11.0 vs. 8.5, p = 0.010) at week 8. Adalimumab dose was escalated to 40 mg weekly in 25 (17.1%) patients, and clinical response and remission were achieved in 40% and 20% of patients at week 56, respectively. Mean faecal calprotectin levels were significantly more decreased in clinical responders compared with non-responders at week 8 (336.3 mg/kg vs. 628.8 mg/kg, p < 0.001). The Fecal calprotectin levels are well correlated with endoscopic severity, and the best cut-off value to predict mucosal healing was 274 mg/kg. The lower endoscopic severity, higher body mass index and higher serum albumin level at baseline were associated with a clinical response at week 8. The lower Mayo score, lower C-reactive protein level, clinical response (74.5% vs. 38.5%, p < 0.001) and mucosal healing (52.7% vs. 30.8%, p = 0.008) at week 8 were associated with clinical response at week 56. Serious adverse drug reactions were identified in 2.7% (4/146) of patients including 1 case of pulmonary tuberculosis. Conclusion Adalimumab is safe and effective for induction and maintenance in Korean patients with UC, regardless of prior anti-TNF therapy. Adalimumab drug level is associated with the efficacy of induction therapy. A better response to induction therapy can predict a better long-term response.
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