Cross-linked Poly(Octadecyl Acrylate)/Polybutadiene Shape Memory Polymer Blends Prepared by Simultaneous Free Radical Cross-linking, Grafting and Polymerization of Octadecyl Acrylate/Polybutadiene Blends.

A semi-crystalline, shape memory polymer (SMP) is fabricated by free radical cross-linking, polymerization, and grafting in a blend of n-octadecyl acrylate and polybutadiene (PB). Poly(n-octadecyl acrylate) (PODA) is a side-chain crystalline polymer, which serves as the structure-fixing network counterbalancing the elastically deformed, cross-linked polymer network. At a constant 50/50 ratio of monomer and polymer the amount of free radical initiator, dicumyl peroxide (DCP) is varied from 1% to 5% w/w PB. From swelling measurements and calculation of the cross-link density it is determined that DCP produces greater than one cross-link per DCP molecule. It is found that lower cross-linking efficiency is favorable for higher shape fixity. This lower efficiency is found to produce a higher degree of crystallinity of the PODA in the 2-5% DCP samples, which is determined to be the main driver of higher shape fixity of the polymer. A SMP with >90% fixity and 100% recovery at uniaxial strains from 34-79% is achieved. This material should be useful for mold processing of shape memory articles. This approach provides a method to decouple the elastomeric and thermoplastic portions of a SMP to convert commodity elastomers into SMPs and tailor the shape memory response.

Comparison of Ultrasound-Guided Percutaneous Polidocanol Injection Versus Percutaneous Ethanol Injection for Treatment of Benign Cystic Thyroid Nodules.

OBJECTIVES: We compared the efficacy, safety, and cost-effectiveness of ultrasound-guided percutaneous polidocanol injection and percutaneous ethanol injection for the treatment of benign cystic and predominantly cystic thyroid nodules. METHODS: A total of 135 cystic thyroid nodules treated by percutaneous ethanol injection and 136 cystic thyroid nodules treated by percutaneous polidocanol injection were enrolled retrospectively in this study from May 2010 to March 2016. The nodules were followed after 1, 3, 6, and 12 months. Nodule volumes, symptoms scores, and cosmetic scores were assessed before treatment and at follow-up. The therapeutic success rate, safety, and cost-effectiveness between the groups were also compared. RESULTS: No significant differences in the reduction of the nodule volume, volume reduction rate, and therapeutic success were observed between the groups with cystic and predominantly cystic thyroid nodules during follow-up (P > .05). Neither the cosmetic scores (P = .59; P = .42) nor the symptom scores (P = .32; P = .73) in the cystic and predominantly cystic nodules were significantly different between the groups at the last follow-up. The complication rates for ethanol were higher than those for polidocanol (P < .05). However, the cost of polidocanol injection was higher than that of ethanol injection for cystic thyroid nodules (mean ± SD, US$97.18 ± US$22.17 versus US$43.36 ± US$5.51; P < .01). CONCLUSIONS: Ultrasound-guided percutaneous polidocanol injection can be an alternative for sclerotherapy of cystic or predominantly cystic thyroid nodules. However, its cost was higher than that of percutaneous ethanol injection.

Synthesis and characterisation of new types of side chain cholesteryl polymers.

A series of cholesterol derivatives have been synthesised via the alkylation reaction of the 3-hydroxyl group with the aliphatic bromide compounds with different chain lengths, namely 3ß-alkyloxy-cholesterol. The double bond between the C5 and C6 positions in these cholesterol derivatives was oxidised into epoxy, followed by an epoxy-ring-opening reaction with the treatment with acrylic acid, resulting in a series of 3ß-alkyloxy-5α-hydroxy-6ß-acryloyloxycholesterol, C(n)OCh (n=1, 2, 4, 6, 8, 10, 12), The acrylate group is connected to the C6 position, which is confirmed by the single crystal structure analysis. The corresponding polymers, PC(n)OCh, were prepared via free radical polymerisation. The structure of monomers and the resulting polymers were characterised with nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). The thermal properties of PC(n)OCh were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). To determine the secondary structure of polymers, circular dichroism (CD) spectra were performed. It was found that not all monomers produce high-molecular-weight polymers because of steric hindrance. However, all polymers have a helical structure, which can be enhanced by increasing the alkoxy chain length. In addition, increasing the alkoxy chain length decreases the glass transition temperature and increases the decomposition temperature of the polymers.