Chiral Polymers from Norbornenes Based on Renewable Chemical Feedstocks

Optically active polymers are of great interest as materials for dense enantioselective membranes, as well as chiral stationary phases for gas and liquid chromatography. Combining the versatility of norbornene chemistry and the advantages of chiral natural terpenes in one molecule will open up a facile route toward the synthesis of diverse optically active polymers. Herein, we prepared a set of new chiral monomers from cis-5-norbornene-2,3-dicarboxylic anhydride and chiral alcohols of various natures. Alcohols based on cyclic terpenes ((-)-menthol, (-)-borneol and pinanol), as well as commercially available alcohols (S-(-)-2-methylbutanol-1, S-(+)-3-octanol), were used. All the synthesized monomers were successfully involved in ring-opening metathesis polymerization, affording polymers in high yields (up to 96%) and with molecular weights in the range of 1.9 × 10⁵-5.8 × 10⁵ (M_w). The properties of the metathesis polymers obtained were studied by TGA and DSC analysis, WAXD, and circular dichroism spectroscopy. The polymers exhibited high thermal stability and good film-forming properties. Glass transition temperatures for the prepared polymers varied from -30 °C to +139 °C and, therefore, the state of the polymers changed from rubbery to glassy. The prepared polymers represent a new attractive platform of chiral polymeric materials for enantioselective membrane separation and chiral stationary phases for chromatography.

Gas-Transport and the Dielectric Properties of Metathesis Polymer from the Ester of exo-5-Norbornenecarboxylic Acid and 1,1′-Bi-2-naphthol

Polymers from norbornenes are of interest for applications in opto- and microelectronic (low dielectric materials, photoresists, OLEDs). Norbornenes with ester motifs are among the most readily available norbornene derivatives. However, little is known about dielectric properties and the gas-transport of polynorbornenes from such monomers. Herein, we synthesized a new metathesis polymer from exo-5-norbornenecarboxylic acid and 1,1′-bi-2-naphthol. The designed monomer was obtained via a two-step procedure in a good yield. This norbornene derivative with a rigid and a bulky binaphthyl group was successfully polymerized over the 1st generation Grubbs catalyst, affording high-molecular-weight products (Mw ≤ 1.5·106) in yields of 94–98%. The polymer is amorphous and glassy (Tg = 161 °C), and it shows good thermal stability. Unlike most, polyNBi is a classic low-permeable glassy polymer. The selectivity of polyNBi was higher than that of polyNB. Being less permeable than polyNB, polyNBi unexpectedly showed a lower value of dielectric permittivity (2.7 for polyNBi vs. 5.0 for polyNB). Therefore, the molecular design of polynorbornenes has great potential to obtain polymers with desired properties in a wide range of required characteristics. Further tuning of the gas separation efficiency can be achieved by attaching an appropriate substituent to the ester and aryl group.

Cocatalyst versus precatalyst impact on the vinyl-addition polymerization of norbornenes with polar groups: looking at the other side of the coin

Polymers derived from norbornenes with polar groups are of interest as modular templates and materials for membrane processes and microelectronic applications due to the attractive combination of their properties.

[Local recurrences of colon cancer (in Russian only)]

AIM

To evaluate the outcomes in patients with local recurrences (LR) of colon cancer.

MATERIAL AND METHODS

Prospective study included 52 patients with local recurrences of colon cancer MR and no distant metastases or disseminated carcinomatosis. Patients have been treated at Ryzhikh State Research Center for Coloproctology for the period 2009-2017. Median of local recurrence was 17.6 months. By the moment of diagnosis, CEA was increased in 24 (46.2%), CA 19-9 - in 4 (7.7%) patients. Forty-eight (92%) patients underwent surgery for local recurrences of colon cancer. In 26 (54%) cases, low ligation of supplying vessel was made during primary tumor excision that was confirmed by significant fragment of intact mesentery of the colon.

RESULTS

Radical surgery for LR was possible in 34 (70.8%) patients, resection of more than one organ was required in 60% of cases. R1-resection was obtained in 12 (25.0%) cases, palliative resections - in 2 (4.2%) patients. Various complications occurred in 34 (70.8%) patients. Additional intraperitoneal chemotherapy was need in 12 (23.1%) cases. Lethal outcomes were absent. Forty-six out of 48 (95.8%) patients were followed-up. Mean follow-up was 19.5 (8.6-34.7) months. Twelve (26.1%) patients were free from recurrent cancer. Only distant metastases developed in 16 (34.8%) patients. Redo LR occurred in 18 (39.1%) patients including 12 of them with distant metastases. Overall 5-year survival was 38%, disease-free survival - 17.5%, median overall survival - 42.8 months, median disease-free survival - 15.2 months. Intraperitoneal chemotherapy did not significantly affect overall survival. Multivariate analysis confirmed high level of CEA and CA 19-9, positive resection margin as negative predictors. Moreover, impaired survival (p=0.03) was noted in case of LR after non-radical surgery for primary tumor with high ligation of the vessel.

CONCLUSION

R0-resection is essential to improve survival and reduce incidence of recurrences. Intraoperative intra-abdominal chemotherapy does not affect the outcomes in patients with LR of colon cancer. Adherence to surgical principles for cancer can reduce the incidence of LR.

[Antigenic divergence in a primary rat hepatocyte culture after exposure to the hepatic carcinogen N-diethylnitrosamine]

Using the indirect immunofluorescence method, the appearance of membrane hetero-organic antigens of kidney origin associated with the Zajdela hepatoma cells was observed on the surface of cells of the rat liver primary culture following a single hepatocarcinogen N-diethylnitrosamine (DENA) treatment before and after explantation. A correlation of antigenic alterations after a single DENA treatment in vivo and in vitro was discovered. No antigens under investigation were discovered in cultured hepatocytes of intact adult rats.