Kind Of Comonomer Research Articles

Novozym 435-Catalyzed Synthesis of Well-Defined Hyperbranched Aliphatic Poly(β-thioether ester).

A series of new hyperbranched aliphatic poly(β-thioether ester)s were prepared by the enzymatic ring-opening polycondensation of 1,4-oxathiepan-7-one (OTO) and AB2/ABB’ comonomer with acid-labile β-thiopropionate groups. Two kinds of comonomers, methyl 3-((3-hydroxy-2-(hydroxymethyl)propyl)thio)propanoate (HHTP) and methyl 3-((2,3-dihydroxypropyl)thio)propanoate (DHTP), with different primary alcohols and secondary alcohols, were synthesized by thiol–ene click chemistry and thiol-ene Michael addition, respectively. Immobilized lipase B from Candida antarctica (CALB), Novozym 435, was used as the catalyst. The random copolymers were characterized by 1H-NMR, 13C-NMR, GPC, TGA, and DSC. All branched copolyesters had high molecular weights over 15,000 Da with narrow polydispersities in the range of 1.75–2.01 and were amorphous polymers. Their degradation properties under acidic conditions were also studied in vitro. The polymeric nanoparticles of hyperbranched poly(β-thioether ester)s were successfully obtained and showed good oxidation-responsive properties, indicating their potential for biomedical applications.

Electrochemical polymerization of carbon fibers and its effect on the interfacial properties of carbon reinforced epoxy resin composites

Polyacrylonitrile (PAN)-based carbon fibers (CFs) were electrochemically deposited and graphene oxide (GO) and three different kinds of comonomers, including diacetone acrylamide (DAAM), acrylic acid (AA) and phenol (Pheno), were electrografted onto CF surfaces. Compared with untreated CFs, the tensile strength of GO-DAAM, GO-AA and GO-Pheno electrografted CFs increased by 5%, 22.6% and 17%, respectively. The surface microstructure of CFs before and after the electropolymerization treatment were subsequently performed by scanning electron microscopy (SEM), Infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), Raman spectrometer (Raman) and surface tension/dynamic contact angle device. With the electrografting of GO-comonomers onto CF surfaces, the characteristic striations along the fiber axis became less well-defined and much more functional groups were introduced onto electrografted CF surfaces. Results also showed that the three-dimensional composite structure was formed through the grafting of GO-intermediate graft polymers onto CF surfaces, which could enhance the final interfacial properties of CF reinforced epoxy composites.

Effects of saturation temperature/pressure on melting behavior and cell structure of expanded polypropylene bead

The expanded polypropylene beads with microcellular structure were prepared by an autoclave-based batch foaming process using non-supercritical CO2 as the foaming agent. Herein, smaller polypropylene micropellets (∼0.6 mm) were obtained from three kinds of polypropylene resin by underwater micro-pelletizer system. The results from differential scanning calorimetry indicated that the double melting peaks of beads moved to higher temperature with increasing saturation temperature and pressure. The kind of comonomer did not exert noticeable influence on the double melting behaviors. The X-ray diffraction of expanded polypropylene bead revealed that characteristic peaks of α-type crystal did not change compared with that of original polypropylene micropellets. The relationship between cell morphology and saturation temperature/pressure of expanded polypropylene beads are discussed preliminarily by scanning electron microscope.

Functional Films of Maleic Anhydride Copolymers under Physiological Conditions

Reactivity and swelling of nanometer films of alternating maleic anhydride copolymers were investigated in dependence on the kind of comonomer and molar mass of copolymer in aqueous solution at pH 7.4 and pH 3.0 in order to reveal their characteristics under physiological conditions. Fully hydrolyzed (maleic acid) chains of the copolymers with styrene, propene, and ethylene comonomers covalently bound to SiO2 substrates showed a "mushroom" swelling behavior at pH 7.4 with a layer thickness scaling of N3/5. Decreasing the environmental pH was found to induce a comonomer-dependent shrinking or collapse of the immobilized polymers due to the change in ionization. From the swelling kinetics of non-hydrolyzed chains, the time constants and characteristics of swelling and anhydride hydrolysis were determined and found to depend on the type of comonomer. The short- and long-term swelling kinetics [l approximately t and approximately ln(t)1/2] were found to be in agreement with theoretical models of polymer swelling, while at intermediate time scales enhanced swelling was observed due to hydrolysis reaction of maleic anhydride groups. The findings elucidate the variety of properties of maleic anhydride copolymer films under physiological conditions, which can advantageously be applied for biofunctionalization of different templates.

Alkaline and Enzymatic Degradation of L‐Lactide Copolymers, 1

Films of poly(L-lactide) [i.e., poly(L-lactic acid) (PLLA)] and L-lactide copolymers with glycolide [P(LLA-GA)(81/19)], epsilon-caprolactone [P(LLA-CL)(82/18)], D-lactide [P(LLA-DLA)(95/5), (77/23), and (50/50)] were prepared and a comparative study on the effects of comonomer type and content on alkaline and proteinase K-catalyzed hydrolyses of the films was carried out. The hydrolyzed films were investigated using gravimetry (weight loss and water absorption), differential scanning calorimetry (DSC), polarimetry, and gel permeation chromatography (GPC). To exclude the effects of molecular weight and crystallinity on the hydrolysis, the films were prepared from polymers having similar molecular weights and made amorphous by melt-quenching. It was found that incorporation of hydrophilic glycolide units in L-lactide chains raises the alkaline and enzymatic hydrolyzabilities, whereas incorporation of hydrophobic epsilon-caprolactone units in L-lactide chains reduces the alkaline and enzymatic hydrolyzabilities. On the other hand, incorporation of D-lactide units with the same hydrophilicity of L-lactide units increases the alkaline hydrolyzability but decreases the enzymatic hydrolyzability. The alkaline hydrolyzability of the films of L-lactide copolymers with different kinds of comonomers and P(LLA-DLA) with different D-lactide unit contents can be closely related to their hydrophilicity. On the other hand, the enzymatic hydrolyzability of L-lactide copolymer films with different kinds of comonomers is mainly determined by hydrophilicity, while that of P(LLA-DLA) films is determined by the averaged L-lactyl and D-lactyl unit sequence lengths. The catalytic effect of proteinase K relative to that of alkali on the hydrolysis of P(LLA-DLA)(77/23) and P(LLA-GA)(81/19) films normalized by that of PLLA was lower than unity, whereas the normalized relative catalytic effect of proteinase K on the hydrolysis of P(LLA-CL)(82/18) film was higher than unity, meaning that despite low absolute alkaline and enzymatic hydrolyzability of the P(LLA-CL)(82/18) film, the catalytic effect of proteinase K may be maintained for this copolymer film, probably because of its blocky structure.

Side chain effects on the thermal properties of ethylene copolymers prepared over metallocene catalyst

Abstract From a study of thylene copolymerization with different comonomers (propylene, 1-butene, 1-hexene, 1-octene) over metallocene catalyst (Cp 2 ZrCl 2 ), the catalytic activity shows an enhancement of the polymerization rate in the presence of comonomers. The thermal properties of the produced copolymers depend on the kind of comonomer and the composition of comonomer in the produced copolymers prepared from copolymerization. Especially, the ethylene copolymers having high comonomer composition from the metallocene catalyst showed that the melting point T m 1 is higher than T m 2 for the polyethylenes from Ziegler-Natta catalyst but not for the ethylene copolymers having low comonomer composition. From differential scanning calorimetry (DSC) analysis, the change of melting temperature with scanning time may be dependent upon the type and composition of comonomer used in copolymerization.

Phenomenological study on sol–gel transition of linear low density polyethylene in organic solvents

Solutions of linear low density polyethylenes in organic solvents formed thermoreversible gels on cooling. Gel-melting temperatures of the polymers in tetralin, decalin, and o-xylene were measured. They increased slowly with increasing polymer concentration. Experimental data were analyzed by the thermodynamic theory of Takahashi, Nakamura, and Kagawa, which is derived for the gel-melting temperature of a crystalline linear copolymer gel. A plot of the gel-melting temperature by the theory depended considerably on the kind of comonomer of the polymer.

Sol-Gel Transitions of Linear Low Density Polyethylenes in Organic Solvents

The sol-gel transitions of linear low density polyethylenes in decalin, tetralin, o-xylene, and toluene were studied. Each sample was a copolymer of ethylene and butene-1, 4-methyl-pentene-1, or octene-1. A thermo-reversible gel was formed for each system and gel-melting temperatures were measured at concentrations of about 4–14 g/100 cm3. It was found experimentally that the gel-melting temperature depended on polymer concentration, molecular weight of the polymer, and the kind of comonomer. Moreover, the structure of crystallite involved in the gel was examined by a polarizing microscope and many spherulites were observed. The data were treated phenomenologically using the thermodynamic theory of Takahashi, Nakamura, and Kagawa, derived for the gel-melting temperature of a crystalline linear copolymer gel. In each solvent, a linear relationship was found to hold between the reciprocal absolute gel-melting temperature 1/Tmg, and ln V2N for samples having a same kind of comonomer, where V2 is the volume fraction of the polymer and N is the weight-average degree of polymerization.

Solution copolymerization of ethylene with ?-olefins by a MgCl2 supported TiCl4 catalyst

Copolymerization of ethylene with α-olefins, i.e. propylene, butene-1, 4-methyl-pentene-1(4-MP-1), was carried out by a MgCl2 supported TiCl4 catalyst in combination with Et3Al at a temperature as high as 170 °C at which the polymerization system was homogeneous. This catalytic system showed very a high activity and produced copolymers having a density of 0.91–0.94 g/ml. Of these three kinds of comonomers, propylene showed the highest reactivity and caused most frequently the termination of a polymer growing by chain transfer reaction and produced copolymers having the broadest MWD.