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The enhanced liver fibrosis (ELF) test is a noninvasive method for diagnosing hepatic fibrosis in patients with nonalcoholic fatty liver disease (NAFLD). This multicenter cohort study aimed to evaluate the accuracy of the ELF test and compare it with other noninvasive tests in Japan.We analyzed 371 Japanese patients with biopsy-proven NAFLD. We constructed area under the receiver operator characteristics curves (AUROC) to determine the diagnostic accuracies of the ELF test, the Mac-2-binding protein glycosylation isomer (M2BPGi), the FIB-4 index, and combinations of these indices.In patients with F0/F1/F2/F3/F4 fibrosis, the median respective values of the ELF test were 8.98/9.56/10.39/10.92/11.41. The AUROCs of the ELF test for patients with F0 vs F1-4, F0-1 vs F2-4, F0-2 vs F3-4, and F0-3 vs F4 fibrosis were 0.825/0.817/0.802/0.812, respectively. The AUROCs of the ELF test were greater than those of the FIB-4 index and M2BPGi at each fibrosis stage. Respective low and high cutoff values yielded sensitivities and specificities for predicting advanced fibrosis (≥F3) of 91.1% and 50.8% and 38.5% and 92.8%, respectively. For F3 or F4 fibrosis, the combined values from the ELF test and FIB-4 index showed a sensitivity of 98.5%, and the combined values from the ELF test and M2BPGi assay showed a specificity of 97.5%.In Japan, the ELF test predicts NAFLD-related fibrosis from its early stages. The diagnostic ability of the ELF test was not inferior to that of other indices, and the combined values of ELF plus other indices were more accurate. This article is protected by copyright. All rights reserved.

Western-style high-fat/high-sucrose diet (HFHSD) changes gut microbiota and bile acid (BA) profiles. Because gut microbiota and BAs could influence each other, the mechanism of changes in both by HFHSD is complicated and remains unclear. We first aimed to clarify the roles of BAs in the HFHSD-induced change of gut microbiota. Then, we studied the effects of the changed gut microbiota on BA composition and liver function. Male wild-type (WT) and human-like Cyp2a12/Cyp2c70 double knockout (DKO) mice derived from C57BL/6J were fed with normal chow or HFHSD for 4 weeks. Gut microbiomes were analyzed by fecal 16S ribosomal RNA gene sequencing, and BA composition was determined by liquid chromatography-tandem mass spectrometry. The DKO mice exhibited significantly reduced fecal BA concentration, lacked muricholic acids, and increased proportions of chenodeoxycholic and lithocholic acids. Despite the marked difference in the fecal BA composition, the profiles of gut microbiota in the two mouse models were quite similar. An HFHSD resulted in a significant increase in the BA pool and fecal BA excretion in WT mice but not in DKO mice. However, microbial composition in the two mouse models was drastically but similarly changed by the HFHSD. In addition, the HFHSD-induced change of gut microbiota inhibited BA deconjugation and 7α-dehydroxylation in both types of mice, which improved chronic liver injury observed in DKO mice. Conclusion: The HFHSD itself causes the change of gut microbiota due to HFHSD, and the altered composition or concentration of BAs by HFHSD is not the primary factor. On the contrary, the gut microbiota formed by HFHSD affects BA composition and ameliorates liver injury in the mouse model with human-like hydrophobic BA composition.

AIM This study aimed to evaluate the real-world efficacy and safety of 12-week sofosbuvir/velpatasvir (SOF/VEL) treatment for patients with decompensated liver cirrhosis caused by hepatitis C virus (HCV) infection. METHODS A total 72 of patients with Child-Pugh (CP) class B or C were enrolled. We evaluated the sustained virologic response at 12 weeks after the end of treatment (SVR12), adverse events (AEs), and changes in the liver function. RESULTS All participants had genotype 1 or 2 HCV infection. At baseline, the numbers of patients with CP class B and C were 59 and 13, respectively. The overall SVR12 rate was 95.8% (69/72); 94.9% (56/59) in CP class B and 100% (13/13) in CP class C. The serum albumin level, prothrombin time and ascites were significantly improved (P

BACKGROUND In clinical trials, a pangenotype direct-acting antiviral (DAA) regimen consisting of glecaprevir (GLE) and pibrentasvir (PIB) exhibited high virologic efficacy and tolerability in patients with hepatitis C virus (HCV) infection. This study sought to confirm these findings in real-world settings, focusing on patients with cirrhosis, history of DAA failure, or HCV genotype 3 who were treated with a 12-week regimen in a large multicenter study from Japan. METHODS In a nationwide multicenter prospective cohort study, we analyzed background characteristics, tolerability, and treatment outcome of patients who underwent a 12-week GLE/PIB regimen. RESULTS Of 1190 patients, 509 (42.8%) underwent the 12-week regimen, and the remaining patients underwent an 8-week regimen. The rate of sustained virologic response (SVR) of patients treated with the 12-week regimen was 99.0%, comparable with that of patients treated with the 8-week regimen. The adverse events were observed in 29.1% of patients. The main adverse event was pruritus, which was observed in 14.7%. Ten patients (2.0%) discontinued therapy during treatment period. CONCLUSION The 12-week GLE/PIB regimen was well-tolerated with high virologic efficacy in patients with cirrhosis, experience of DAA, or HCV genotype 3; tolerability and SVR rate were comparable with those of DAA-naive, non-cirrhotic, non-genotype 3 patients who underwent 8-week regimen.

Based on high efficacy and safety demonstrated in clinical trials, treatment with glecaprevir/pibrentasvir (G/P) for 8 weeks is recommended for hepatitis C virus (HCV)-infected patients who are direct-acting antiviral (DAA) naïve, genotype 1 or 2, and noncirrhotic. The aim of this study was to validate real-world experience with 8-week G/P treatment in Japan. We conducted a prospective observational cohort study in 554 patients who underwent 8-week treatment from among 1,022 patients who initiated G/P therapy. The majority (54.5%) were male, with a median age of 66 years, and HCV genotype distribution was genotype 1, 43.8%; genotype 2, 55.3%; and mixed subtype, 0.9%. Overall, the sustained virologic response rate at 12 weeks (SVR12) was 92.8% (530/571) in the intention-to-treat population and 99.3% (526/530) in the per-protocol population. The SVR12 rates by subgroups were as follows: subtype 1a, 100% (6/6); 1b, 100% (189/189); 2a, 99.3% (150/151); 2b, 99.0% (103/104); and mixed subtype, 50% (2/4). Among four patients with virologic failure following 8-week treatment with G/P, none had baseline polymorphisms or treatment-emergent amino acid substitutions in NS3. However, 2 of 4 patients with virologic failure had treatment-emergent amino acid substitutions in NS5A. Adverse events (AEs) were reported in 21.5% of patients and 1.2% of patients discontinued due to drug-related AEs. In conclusion, G/P treatment for 8 weeks was safe and effective for DAA-naïve noncirrhotic genotype 1 or 2 patients in a real-world clinical setting in Japan.

BACKGROUND Patients with chronic hepatitis C are often complicated by chronic kidney disease (CKD). AIM To evaluate the efficacy, safety and pharmacokinetics of glecaprevir/pibrentasvir in patients with severe renal impairment. METHODS In a prospective, multicentre study involving 35 medical institutions, 832 genotype 1-3 patients were treated with glecaprevir/pibrentasvir. The efficacy and safety of glecaprevir/pibrentasvir were analysed for patients with CKD stage 4 or 5. Multivariate analysis was performed to identify the factors associated with the most frequently observed adverse event. In patients undergoing haemodialysis, a pharmacokinetic study was conducted to investigate the dialysability of the drugs: plasma samples were obtained from the arterial and venous sides of a dialyser to serially measure drug concentrations. RESULTS The subjects comprised 141 patients (32 with CKD stage 4 and 109 with CKD stage 5), of whom 100 were undergoing haemodialysis. All but one stage 5 CKD patients undergoing haemodialysis achieved sustained virologic response (99.3%). Adverse events were observed in 39.7% of subjects: pruritus was the most frequent (30.5%), and was significantly associated with haemodialysis. In the pharmacokinetic study, no arterial-venous differences in the plasma concentrations of glecaprevir/pibrentasvir were detected during the haemodialysis sessions. CONCLUSIONS Glecaprevir/pibrentasvir was highly effective and safe in chronic hepatitis C patients with severe renal impairment. Haemodialysis was associated with increased incidence of pruritus, which was the most frequent adverse event, but had little or no influence on the drug concentrations, which indicated that their dialysability is very low and that no dose modification is required in patients undergoing haemodialysis. (UMIN registration no. 000032073).

Aim Although the development of new direct-acting antivirals (DAAs) for the treatment of chronic hepatitis C virus (HCV) infection has markedly advanced, the effects of cirrhosis on DAA treatment remain unclear. We aimed to clarify the impact of cirrhosis on DAA treatment of patients infected with HCV. Methods This large-scale, multicenter, retrospective study consisted of 2130 HCV genotype 1b-infected patients who were treated with one of the following DAA combination therapies: asunaprevir/daclatasvir (ASV/DCV), ledipasvir/sofosbuvir (LDV/SOF), or paritaprevir/ombitasvir/ritonavir (PTV/OBV/r). Ninety-two patients (4.3%) previously received DAA-based treatment. Seven hundred and forty-five patients (34.9%) had cirrhosis. Results Overall, the sustained virologic response (SVR) rate was 93.0%. The SVR rates in patients who received ASV/DCV, LDV/SOF, or PTV/OBV/r were 90.0%, 96.9%, and 97.6%, respectively. The SVR rate in patients with cirrhosis (89.1%) was significantly lower than that in patients without cirrhosis (95.1%, P = 6.94 × 10-7 ). In the multivariate analysis for the overall cohort, absence of cirrhosis (P = 1.26 × 10-3 ), no previous DAA-based treatment (P = 2.54 × 10-14 ), low HCV-RNA levels (P = 1.64 × 10-6 ), wild-type non-structural protein 5A L31/Y93 (P = 7.33 × 10-13 ), and DAA regimen (LDV/SOF or PTV/OBV/r) (P = 1.92 × 10-14 ) were independent factors contributing to SVR. Except for patients with DAA-based treatment history, absence of cirrhosis (P = 2.15 × 10-3 ; odds ratio, 2.51) was an independent factor contributing to SVR in 2038 DAA-naive patients. Conclusion This study suggests that the presence of cirrhosis reduces the SVR rate of DAA treatment, regardless of the type of DAA treatment.

AIM The aim of this study was to clarify the effects and safety of ombitasvir/paritaprevir/ritonavir (OBT/PTV/r) therapy in genotype 1b chronic hepatitis C patients with non-dialysis chronic kidney disease (CKD). METHODS This retrospective, multicenter study of 12-week OBT/PTV/r therapy included genotype 1b patients with non-dialysis CKD. Chronic kidney disease was defined as an estimated glomerular filtration rate (eGFR)

Background and aim This study aimed to clarify the factors predictive of treatment response to tolvaptan (V2-receptor antagonist) for cirrhotic patients with hepatic edema in a real-world setting. Methods In this retrospective, multicenter study, tolvaptan was orally administered at a dose of 7.5 mg once a day. Patients with a decrease in body weight of 1.5 kg or greater from baseline were characterized as responders at day 7. Results Of 229 patients, 210 were subjected to this analysis. Patients consisted of 133 men and 77 women, with the median age of 67 years (range, 40-89 years). According to the Child-Pugh classification, five patients were classified as class A, 90 as class B, and 115 as class C. The frequencies of responders and nonresponders were 55.2% and 44.8%, respectively. Blood urea nitrogen (BUN) level was significantly lower in responders compared with nonresponders (P = 3.77 × 10-3 ). Using the receiver operating characteristic curve, the cutoff value of 28.2 mg/dL was the most useful in discriminating responders from nonresponders. Among 154 patients with BUN level of less than 28.2 mg/dL, 95 (61.7%) were responders. By contrast, among 56 patients with BUN level of 28.2 mg/dL or more, 21 (37.5%) were nonresponders (P = 2.70 × 10-3 ). On multivariate analysis, BUN level of 51 mEq/day were found to be independent factors associated with the response to tolvaptan. Conclusions This study suggests that BUN level and urinary sodium excretion are closely associated with the response to tolvaptan in cirrhotic patients with hepatic edema.

The gut microbiota (GM) play a central role in their host's metabolism of bile acids (BAs) by regulating deconjugation, dehydroxylation, dehydrogenation, and epimerization reactions to generate unconjugated free BAs and secondary BAs. These BAs generated by the GM are potent signaling molecules that interact with BA receptors, such as the farnesoid X receptor and Takeda G-protein-coupled receptor 5. Each BA has a differential affinity to these receptors; therefore, alterations in BA composition by GM could modify the intensity of receptor signaling. Bile acids also act as antimicrobial agents by damaging bacterial membranes and as detergents by altering intracellular macromolecular structures. Therefore, BAs and the GM reciprocally control each other's compositions. In this review, we discuss the latest findings on the mutual effects of BAs and GM on each other; we also describe their roles in the pathophysiology of liver disease progression and potential therapeutic applications of targeting this cross-talk.

Aim From a pharmacokinetic viewpoint, ombitasvir/paritaprevir/ritonavir, one of the standards of care for genotype 1b chronic hepatitis C in Japan, could be possible in patients with impaired renal function. The aim of this study was to assess the efficacy and safety that have not yet been addressed in patients undergoing dialysis. Methods A retrospective, multicenter study evaluated the outcome of 12-week ombitasvir (NS5A inhibitor)/paritaprevir (NS3/4A protease inhibitor)/ritonavir combination therapy for dialysis patients. The primary endpoint was sustained virologic response 12 weeks after therapy (SVR12). Results The subjects were 31 patients aged 63 years (range, 49–85 years) including 10 cirrhotic patients. All of the 31 patients had an estimated glomerular filtration rate level

Aim Protease inhibitors with pegylated interferon (PEG IFN)/ribavirin improve a sustained virological response (SVR) rate to approximately 90% in chronic hepatitis C genotype 1b patients with IL28B rs8099917 genotype TT, but yield only approximately 50% in those with the unfavorable non-TT. Among such treatment-refractory patients, serum vitamin D levels could influence the SVR rate. This randomized controlled trial was conducted to assess the effect of native vitamin D supplementation in simeprevir with PEG IFN/ribavirin for 1b patients with non-TT. Methods Patients were randomly assigned to receive simeprevir (100 mg/day) for 12 weeks plus PEG IFN/ribavirin for 24 weeks (control group, n = 58), or vitamin D (2000 IU/day) for 16 weeks including a lead-in phase plus PEG IFN/ribavirin for 24 weeks (vitamin D group, n = 57). The primary end-point was sustainably undetectable viremia 24 weeks after the end of treatment (SVR). Results SVR rates were 37.9% in the control group and 70.2% in the vitamin D group. In subgroup analysis, SVR rates of prior null responders were 11.8% and 54.5%, respectively. SVR rates for advanced fibrosis were 28.6% and 65.4%. SVR rates for patients with vitamin D3 deficiency at the baseline were 25.0% in the control group and 66.7% in the vitamin D group. Overall, the SVR rate was significantly higher in patients with high serum 25(OH)D3 levels at the beginning of combination therapy than in those with low serum 25(OH)D3 levels. Conclusion Native vitamin D3 supplementation improved SVR rates in simeprevir with PEG IFN/ribavirin for chronic hepatitis C genotype 1b patients with refractory factors.

AIM Proton beam therapy is safe and more effective than conventional radiation therapy for the local control of nodular hepatocellular carcinoma (HCC). However, evaluating therapeutic response by imaging is not accurate during the early post-irradiation period. Therefore, we examined whether the histopathological study of biopsy specimens obtained at 3 weeks after irradiation can be used to more accurately assess therapeutic response. METHODS Fifteen HCC lesions from 13 patients were treated with proton beam irradiation. Tissue biopsy samples were obtained using abdominal ultrasound-guided percutaneous fine-needle aspiration from the center of the tumor before, 3 weeks after and 1 year post-proton therapy. The specimens were examined after staining with hematoxylin-eosin (HE) and a MIB-1 antibody. RESULTS MIB-1 labeling indices (LI) before treatment were 13.0 ± 8.5% (mean ± SD; range, 0.6-27.0), whereas those 3 weeks after proton therapy were significantly reduced to 3.2 ± 2.4% (range, 0.6-8.9) (P

Aim: Non-alcoholic fatty liver disease (NAFLD) that encompasses a spectrum of liver disorders characterized by simple steatosis, non-alcoholic steatohepatitis (NASH) through cirrhosis, is becoming an important chronic liver disease in Japan. Currently, there is no proven therapy for NASH. In this study, we assessed the efficacy of statin therapy in NASH patients with dyslipidemia. Methods: Twenty patients with biopsy-proven NASH with dyslipidemia who agreed to participate in this multicentric prospective study were enrolled. The patients were treated for 12 months with pitavastatin 2 mg/day. Clinical and histological alterations were comparatively evaluated before and after treatment. Standard weight loss counseling was continued during the treatment period. Follow-up liver biopsy was performed in 13 patients. Results: Twenty-five percent of patients had hyperlipoproteinemia type IIa and 75% had hyperlipoproteinemia type IIb at baseline. The levels of alanine aminotransferase, γ-glutamyl transpeptidase and lipid profiles were significantly improved by the treatment with pitavastatin for 12 months. Especially, these improvements were prominent in NASH patients with hyperlipoproteinemia type IIb. While non-alcoholic fatty liver disease activity score and fibrosis stage did not change significantly in all patients, they did improve in 54% and 42% in individual patients, respectively. Conclusion: NASH-related metabolic parameters improved with therapy including histology in some patients. However, three of 13 patients had progression of fibrosis during the treatment. Our pilot study demonstrated the efficacy of pitavastatin for the treatment of NASH with dyslipidemia, especially with hyperlipoproteinemia type IIb and controlled trials are needed in the future.

AIM Infection with hepatitis C virus (HCV) is the leading cause of liver cirrhosis that develops into hepatocellular carcinoma. Previous studies have shown in vitro that lipids within hepatocytes are crucially important for a series of HCV infection-proliferation-release processes. On the other hand, in the patients with HCV, the serum total cholesterol (Total-C) and low-density lipoprotein cholesterol (LDL-C) levels have been reported to be lower. We conducted an epidemiological survey of a large cohort and investigated whether the lower serum lipid levels were caused by a direct or the secondary effects of HCV infection (i.e. hepatic damage or nutritional disorder). METHODS Among 146 857 participants (male, 34%; female, 66%) undergoing public health examinations between 2002 and 2007 in Ibaraki Prefecture, Japan, the HCV positive rates determined by HCV antibody/antigen and/or RNA tests were 1.37% and 0.67% in males and females, respectively. RESULTS In addition to Total-C and LDL-C, serum high-density lipoprotein cholesterol and triglyceride concentrations were also significantly lower in the HCV positive subjects compared with the negative subjects, regardless of sex, age or nutritional state evaluated by body mass index. Multivariate analysis showed that HCV infection was the strongest among the factors to be significantly associated with the lower level of these lipids. Particularly, the hypolipidemia was also confirmed in the HCV positive subjects with normal aminotransferase levels (alanine aminotransferase ≤30 and aspartate aminotransferase ≤30). CONCLUSION This epidemiological survey in a large Japanese cohort suggests that the HCV infection itself might directly cause hypolipidemia, irrespective of host factors including age, hepatic damage and nutritional state.

Aim: Although the anti-hepatitis C virus (HCV) antibody test has been recommended to the whole Japanese population, most countries have not implemented it. The present study aims to re-evaluate the usefulness of markers examined in the general health examination for the initial screening of HCV carriers. Methods: Of the overall population, 25 142 individuals (8876 males, 16 266 females) participated in health examinations with HCV tests in 2005, and the most commonly associated markers for HCV-positive subjects were explored by multivariate analysis, based on blood biochemical, physical, sphygmomanometric and hematological parameters. Thereafter, the efficiencies of the markers were estimated from a total population of 85 013 individuals (29 502 males, 55 511 females) in 2003–2005. Results: The most significantly associated markers for HCV positivity were aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Optimal limits of ALT and AST by receiver–operator characteristic (ROC) analysis were 24 and 27 IU (male, 33 and 28 IU; female, 22 and 26 IU), respectively. However, one-quarter of HCV carriers were not found to be positive using the optimal limits of aminotransferases. Conclusion: The present study confirmed the limitation of serum aminotransferase levels as markers of HCV for primary screening. Therefore, at present, an anti-HCV antibody test is required for the efficient screening of HCV carriers in all health examinations.

Background: Relationships between impairment, disability and handicap in neurological diseases such as stroke and spinal cord injury have been studied using the framework of the international classification of impairment, disability and handicap, defined by World Health Organization. Those relationships in Parkinson's disease have rarely been studied on a statistical basis. Methods: In order to identify relationships between impairment, disability, handicap, burden of care, economic expenses and neurophysiological dysfunction in patients with Parkinson's disease, we made quantitative evaluations of these parameters in 24 patients and 14 care-givers. Impairment was measured by symptomatic assessment for motor and autonomic impairments and neuropsychological assessment using the revised version of Hasegawa's dementia scale, the mini-mental state examination, and the self-rating depression scale. Disability was measured by Hoehn and Yahr scale, Barthel index, and the comprehensive activities of daily living index for the elderly. Handicap was measured by the Craig handicap assessment and reporting technique. Scores for burdens of care on principal care-givers had physical and psychosocial aspects. Neurophysiological dysfunction was studied by measuring visual event-related potentials and regional cerebral blood flow. Results: Motor and cognitive impairments, disability and handicap significantly correlated to each other. In particular, disability and handicap were strongly correlated. The burden of care on care-givers, economic expenses, visual event-related potentials and regional cerebral blood flow were significantly correlated with impairment, disability and handicap. Conclusion: Further investigations are anticipated to confirm practical values of symptomatic, neuropsychological, electrophysiological and neuroimaging evaluations to predict burden of care on families and economic expenses for patients with Parkinson's disease.

The polymerization of the complex of methyl methacrylate with stannic chloride, aluminum trichloride, or boron trifluoride was carried out in toluene solution at several temperatures in the range of 60° to −78°C by initiation of α,α′-azobisisobutyronicrile or by irradiation with ultraviolet rays. The tacticities of the resulting polymers were determined by NMR spectroscopy. Both the 1:1 and the 2:1 methyl methacrylate–SnCl4 complexes gave polymers with similar tacticities at the polymerization temperatures above −60°C. With decreasing temperature below −60°C, the isotacticity was more favored for the 2:1 complex, whereas the tacticities did not change for the 1:1 complex. On the ESR spectroscopy of the polymerization solution under the irradiation of ultraviolet rays at −120°C, the 1:1 SnCl4 complex gave a quintet, while the 2:1 SnCl4 complex gave both a quintet and a sextet. The sextet became weaker with increasing temperature and disappeared at −60°C. This behavior of the sextet corresponds to the change of the tacticities of polymer for the 2:1 SnCl4 complex. An intra–intercomplex addition was suggested for the polymerization of the 2:1 complex, which took a cis-configuration on the basis of its infrared spectra. The sextet can be ascribed to the radical formed by the intracomplex addition reaction, while the quintet can correspond to that formed by the intercomplex addition reaction. The proportion of the intracomplex reaction was estimated to be about 0.25 at −75°C, and the calculated value of the probability of isotactic diad addition of the intracomplex reaction was found to be almost unity.

The effect of complex formation on stereoregulation in free-radical polymerization was studied. Complexes of methacrylonitrile with ZnCl2 and SnCl4 were prepared and their properties and structures examined. The complexes were polymerized by initiation of α,α′-azobisisobutyronitrile or by irradiation with γ-rays from a60Co source or ultraviolet rays either in solution or in bulk at various temperatures ranging from −78 to 100°C. The triad tacticities of the resulting polymethacrylonitrile were determined by converting it to poly(methyl methacrylate) for NMR spectroscopy. The radicals in complexed forms were studied by ESR spectroscopy with the polymerization system in toluene irradiated with ultraviolet rays at −120°C. The tacticities of the resulting polymers and their dependencies on the polymerization temperature were found to be characteristic of the complex species, i.e., the kind of metal chloride and the stoichiometry, being different from the tacticities and the dependencies, respectively, of the polymer obtained with pure methacrylonitrile. The 2:1 and the 1:1 complexes with SnCl4 were found to give an eleven-line and a nine-line spectrum, respectively. On the basis of the results of both the tacticities and the ESR spectra, it was estimated that the proportion of the intracomplex reaction was 40%, and that the probabilities of isotactic diad addition of intra- and intercomplex reaction were 0.70 and 0.48, respectively.

The 1:1 or 2:1 complex of acrylonitrile, methacrylonitrile, or methyl methacrylate with ZnCl2 was copolymerized with styrene at the temperature of 0–30°C without any initiator. The structure of the copolymer from methyl methacrylate complex and styrene was examined by NMR spectroscopy. The complexes of acrylonitrile or methacrylonitrile with ZnCl2 gave a copolymer containing about 50 mole-% styrene units. The complexes of methyl methacrylate yielded an alternating copolymer when the feed molar ratio of methyl methacrylate to styrene was small, but with increasing feed molar ratio the resulting copolymer consisted of about 2 moles of methyl methacrylate per mole of styrene. The formation of a charge-transfer complex of styrene with a monomer coordinated to zinc atom was inferred from the ultraviolet spectra. The regulation of the copolymerization was considered to be effected by the charge-transfer complex. The copolymer resulting from the 2:1 methyl methacrylate–zinc chloride complex had no specific tacticity, whereas the copolymer from the 1:1 complex was richer in coisotacticity than in cosyndiotacticity. The change of the composition of the copolymer and its specific tacticity in the polymerization of the methyl methacrylate complex is related to the structure of the complex.

Complexes of methyl methacrylate and methacrylonitrile with Lewis acids (SnCl4, AlCl3, and BF3) were copolymerized with styrene at −75°C under irradiation with a high-pressure mercury lamp in toluene solution. The resulting copolymers consisted of equimolar amount of methyl methacrylate or methacrylonitrile and styrene, regardless of the molar ratio of monomers in the feed. NMR spectroscopy showed the copolymers to have an alternate sequence. The tacticities of the copolymers varied with the complex to have an alternate sequence. The tacticities of the copolymers varied with the complex species: the copolymer from the SnCl4 complex system had a higher cosyndiotactieity, while those from the AlCl3 and the BF3 complex systems showed coisotacticity to predominate over cosyndiotacticity. NMR spectroscopic investigation of the copolymerization system indicated the presence of a charge-transfer complex between the styrene and the methyl methacrylate coordinated to SnCl4. The concentration of the charge-transfer complex was estimated to be about 30% of monomer pairs at −78°C at a 1:1 molar ratio of feed. The growing end radicals were identified as a methyl methacrylate radical for the AlCl3 complex–styrene system and a styrene radical for the SnCl4 complex–styrene system by the measurement of the ESR spectra of the copolymerization systems under or after irradation with a high-pressure mercury lamp. The tacticity of the resulting polymer appears to be controlled by the structure of the charge transfer complex. In the case of the SnCl4 complex a certain interaction of SnCl4 with the growing end radical seems to be a factor controlling the polymer structure. These copolymerizations can be explained by an alternating charge-transfer complex copolymerization scheme.