Comonomer Feed Ratio Research Articles

Study on Rheological Behaviors of Ultrafine CaCO3 Aqueous Suspensions Modified with Acrylate Macromolecular Modifiers

By varying the feed ratios of comonomers, butyl acrylate (BA), acrylic acid (AA), and methyl methacrylate (MMA), four acrylate macromolecular modifiers (AC730, AC532, AC235, and AC037) were synthesized by free radical copolymeration in ethnol. The effect of these modifiers on rheological behaviors of ultrafine CaCO3 aqueous suspensions was investigated on the basis of a series of rheological measurements. The results showed that comonomer compositions and amounts of modifiers have obvious effect on rheological behaviors of CaCO3 aqueous suspensions. In the case of AC730 and 0.2-0.4 parts of AC532, suspensions were pseudoplastic fluids, exhibiting shear thinning behavior; while in the case of AC235, AC037 and 0.6-1.4 parts of AC532, suspensions were dilatant fluids, exhibiting shear thickening behavior. Except the suspensions modified by 1.2 and 1.4 parts of AC730, the rheological data of other suspending systems could be well correlated with Herschel-Bulkley model. Optimum amounts of different modifiers were determined on the basis of rheological analysis, 0.8 parts for AC730, 0.6 parts for AC532 or AC235, and 0.4 parts for AC037.

Novel cationic poly(ester-co-carbonate) materials functionalized with tertiary amine groups

The current study aimed at designing cationic and biodegradable biomaterials with improved biological functionality. We report the enzymatic synthesis, characterization and preliminary biological assessment of a series of novel functionalized poly(ester-co-carbonate)s, namely [poly(ADMC-co-CL)]s containing tertiary amine groups in the backbone. The copolymer compositions agreed very well with the feed ratios of co-monomers, indicating the excellent controllability of the preparation method. Static contact angle measurement revealed that the hydrophilicity of copolymers can be tailored and gradually increased with an increasing ADMC content in copolymers. With respect to the weight loss, in vitrodegradation tests demonstrated the occurrence of lipase-dependent degradation. Copolymers with a higher ADMC content degraded far faster as well. Cell proliferation tests suggested that the incorporation of ADMC in copolymers would considerably promote cell adhesion and proliferation on the polymer surface, indicative of good biocompatibility. As a demonstration of a potential application, poly(ADMC–co-CL) microspheres were fabricated in an attempt to construct a controlled delivery system for the drug ibuprofen. The sustained release of ibuprofen loaded in the copolymers was found to have an evident acceleration in acidic conditions, indicating the pH dependence of such release behavior.

Toward Functionalization of Thermoresponsive Poly(N-vinyl-2-pyrrolidone)

A series of new monomers with different substituents at the 3-position of N-vinyl-2-pyrrolidone (NVP) were synthesized. The substituents include simple alkyl (methyl, ethyl, propyl, and isopropyl), ether (methoxy ethyl and ethoxy ethyl), and functional groups (e.g., aldehyde, epoxy, and acetylene). These monomers were (co)polymerized radically to produce a family of (co)polymers based on poly(N-vinyl-2-pyrrolidone) (PVP), and the copolymer compositions could be controlled through varying comonomer feed ratio. When the monomers are substituted with ethyl-, methyl-, or ether-containing alkyl chains, their homopolymers are soluble in cold water but display sensitive and reversible phase transition upon heating to a cloud point temperature (CP). Control over CP of homopolymers was achieved by changing the hydrophilicity of the substituents. CP could also be tuned by copolymerization of different monomers or adding NaCl to the polymer aqueous solution. The mechanism of the thermoresponsive properties was studied by temperature-dependent 1H NMR and microcalorimetry. The results confirmed that the phase transitions of (co)polymers bearing ether substituents were less cooperative with lower phase transition enthalpy and less dehydration even at temperatures well above the CP, and the transition is predominately liquid to liquid. In addition, aldehyde, epoxy, and acetylene groups were introduced to the (co)polymer chains as reactive groups; model reactions of these groups with other molecules were very efficient and simple. Thus, these polymers can subsequently be modified to impart additional functionality to be used as thermoresponsive polymers for bioconjugation. Finally, these polymers are demonstrated to be at least as biocompatible as PVP.

Highly Active Living Random Copolymerization of Norbornene and 1-Alkene with ansa-Fluorenylamidodimethyltitanium Derivative: Substituent Effects on Fluorenyl Ligand

Copolymerizations of norbornene with propylene and 1-octene were conducted with a series of ansa-fluorenylamidodimethyltitanium complexes, [t-BuNSiMe2Flu]TiMe2 (1), [t-BuNSiMe2(3,6-tBu2Flu)]TiMe2 (2), [t-BuNSiMe2(2,7-tBu2Flu)]TiMe2 (3), and [t-BuNSiMe2(C29H36)]TiMe2 (4; C29H36, octamethyloctahydrodibenzofluorenyl), activated by trialkylaluminum-free modified methylaluminoxane. The catalytic systems promoted random copolymerizations in a living manner regardless of the titanium complex used. The activity increased by the introduction of the tBu groups on the Flu ligand, and 4 showed the highest activity for each copolymerization. The comonomer content of the copolymers obtained was controllable in a wide range by changing comonomer feed ratio with these catalytic systems. The linear relationships were observed between the norbornene content and the glass transition temperature of the copolymer, whereas the slopes depended on the titanium complex used. The result suggested that the titanium complexes affected the microstructures of the copolymers produced. The evaluation of the monomer reactivity ratios in the copolymerization of norbornene with 1-octene indicates a preference for the norbornene insertion regardless of the last inserted monomer unit in growing polymer chain in all the catalytic systems.

Thermally Responsive P(M(EO)2MA-co-OEOMA) Copolymers via AGET ATRP in Miniemulsion

Thermally responsive random copolymers of di(ethylene glycol) methyl ether methacrylate (M(EO)2MA) and oligo(ethylene glycol) methyl ether methacrylate (OEOMA) (Mn ∼ 300 or 475) with varied compositions were successfully synthesized via activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) in miniemulsion at 65 °C. The copolymerizations were controlled, generating well-defined copolymers with relatively narrow molecular weight distribution (Mw/Mn ∼ 1.3−1.5). Because of the relatively high reaction temperature (65 °C), OEOMA was confined into oil phase, although OEOMA was miscible with water in all proportions at room temperature. The compositional study proved that the composition of the copolymers reflected the comonomer feed ratio. The cloud point of the resulting copolymer increased proportionally with the OEOMA molar content. Microgels of P(M(EO)2MA-co-OEOMA) were also prepared by addition of ethylene glycol dimethacrylate (EGDMA) cross-linker. Similar to their linear analogues, the phase transition temperature of the copolymer microgels can be tuned by changing OEOMA content in the microgels.

Synthesis and characterizations of degradable aliphatic-aromatic copolyesters from lactic acid, dimethyl terephthalate and diol: Effects of diol type and monomer feed ratio

Lactic acid-based aliphatic/aromatic copolyesters are synthesized to incorporate the degradability of polylactic acid and good mechanical properties of aromatic species by using polycondensation of lactic acid (LA), dimethyl terephtha- late (DMT), and various diols. Effects of diol lengths and comonomer feed ratios on structure and properties of the result- ing copolymers are investigated. Three types of diols with different methylene lengths are employed, i.e., ethylene glycol (EG), 1,3-propanediol (PD) and 1,4-butanediol (BD). LA/DMT/diol feed ratios of 2:1:2, 1:1:2, and 1:2:4 are used in each diol system. It is found that types of the diols play an important role in the properties of the copolyester, where an increase in diol length results in an increase in the copolymers molecular weight, and a decrease in Tg, Tm and crystallinity, when a constant monomer feed ratio is employed. Monomer feed ratio also has a significant effect on properties of the copolymers, where an increase in the aromatic content leads to formation of copolymers with higher molecular weight, longer aromatic block sequence and high aromatic to aliphatic ratio in the chain structure. These, in turn, lead to an increase in Tg, Tm, crys- tallinity and thermal stability of the copolymer samples, and a reduction in their solubility.

Stereoregular Methacrylate-POSS Hybrid Polymers: Syntheses and Nanostructured Assemblies

This contribution reports the first examples of stereoregular (isotactic, it-, and syndiotactic, st-) methacrylate-POSS (polyhedral oligomeric silsesquioxane) hybrid polymers and their derived nanostructured assemblies. The polymerization of methyl methacrylate (MMA) by isospecific and syndiospecific living metallocene catalysts, when end-capped with methacrylisobutyl POSS (MA-POSS) or simultaneously copolymerized with MA-POSS at ambient temperature, readily produces highly stereoregular (94% it- and st-) MA-POSS end-capped PMMA (PMMA-POSS) or statistical copolymers PMMA-co-P(MA-POSS). The MA-POSS incorporation in the it-copolymers ranges from a low 2.6 mol % (20 wt %) to a high, maximum 24 mol % (75 wt %), whereas the incorporation in the st-copolymers is relatively lower with the same comonomer feed ratio due to the formation of a crystalline inclusion complex in which the POSS nanocages are encapsulated within the helical st-PMMA cavity. The it-copolymers with high POSS contents (>20 mol %) show evidence for interchain association through POSS aggregation and display a ∼20 °C Tg enhancement over the pristine it-PMMA. MA-POSS end-capped diastereomeric PMMAs exhibit versatile nanostructured assemblies, including micelle-like core−shell nanostructures (Rh up to 186 nm derived from the 5.7 nm it-PMMA-POSS unimer) through POSS inorganic collapse in selective solvents, helical stereocomplexes (Rh = 11 nm) between two or three polymer chains through organic self-organization of the diastereomeric PMMAs, and large core−shell nanospheres (Rh up to 636 nm) through synergistic organic PMMA self-organization and inorganic POSS nanocluster aggregation. Thermal annealing of the it-/st-PMMA-POSS blend in a 1:2 ratio also generates the crystalline stereocomplex with a high Tm of 213 °C.

Copolymerization of norbornene and 5‐norbornene‐2‐yl acetate using novel bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3/AlEt3 catalytic system

AbstractVinyl‐type copolymerization of norbornene (NBE) and 5‐NBE‐2‐yl‐acetate (NBE‐OCOMe) in toluene were investigated using a novel homogeneous catalyst system based on bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3/AlEt3. The copolymerization behavior as well as the copolymerization conditions, such as the levels of B(C6F5)3 and AlEt3, temperature, and monomer feed ratios, which influence on the copolymerization were examined. Without combination of AlEt3, the catalytic bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3 exhibited very high catalyst activity for polymerization of NBE. Combination of AlEt3 in catalyst system resulted in low conversion for polymerization of NBE. For copolymerization of NBE and NBE‐OCOMe, involvement of AlEt3 in catalyst is necessary. Slight addition of NBE‐OCOMe in copolymerization of NBE and NBE‐OCOMe gives rise to significant increase of catalyst activity for catalytic system bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3/AlEt3. Nevertheless, excess increase of the NBE‐OCOMe content in the comonomer feed ratios results in decrease of conversion as well as activity of catalyst. The achieved copolymers were confirmed to be vinyl‐addition copolymers through the analysis of FTIR, 1H NMR, and 13C NMR spectra. 13C NMR studies further revealed the composition of the copolymer and the incorporation rate was 7.6–54.1 mol % ester units at a content of 30–90 mol % of the NBE‐OCOMe in the monomer feeds ratios. TGA analysis results showed that the copolymer exhibited good thermal stability (Td > 410 °C) and failed to observe the glass transitions temperature over 300 °C. The copolymers are confirmed to be noncrystalline by WAXD analysis results and show good solubility in common organic solvents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3990–4000, 2009

Synthesis and biodegradability of l-lactide/glycidol copolymers

Abstract Random copolymers of l -lactide (LA) and glycidol (G) were systematically synthesized via ring-opening polymerization (ROP). It was found that thermal properties of copolymers were strongly dependent on polymer composition which was successively controllable by changing comonomer feed ratio. The effects of polymerization conditions as well as polymer compositions on polymer properties were thoroughly studied. The biodegradation and enzymatic hydrolysis of copolymers were also examined. It was found that the biodegradability by an activated sludge of L/G copolymers was strongly affected by both polymer composition and crystallinity whereas their hydrolyzability by proteinase K was merely influenced by polymer composition.

Comparison of Facially Amphiphilic versus Segregated Monomers in the Design of Antibacterial Copolymers

A direct comparison of two strategies for designing antimicrobial polymers is presented. Previously, we published several reports on the use of facially amphiphilic (FA) monomers which led to polynorbornenes with excellent antimicrobial activities and selectivities. Our polymers obtained by copolymerization of structurally similar segregated monomers, in which cationic and non-polar moieties reside on separate repeat units, led to polymers with less pronounced activities. A wide range of polymer amphiphilicities was surveyed by pairing a cationic oxanorbornene with eleven different non-polar monomers and varying the comonomer feed ratios. Their properties were tested using antimicrobial assays and copolymers possessing intermediate hydrophobicities were the most active. Polymer-induced leakage of dye-filled liposomes and microscopy of polymer-treated bacteria support a membrane-based mode of action. From these results there appears to be profound differences in how a polymer made from FA monomers interacts with the phospholipid bilayer compared with copolymers from segregated monomers. We conclude that a well-defined spatial relationship of the whole polymer is crucial to obtain synthetic mimics of antimicrobial peptides (SMAMPs): charged and non-polar moieties need to be balanced locally, for example, at the monomer level, and not just globally. We advocate the use of FA monomers for better control of biological properties. It is expected that this principle will be usefully applied to other backbones such as the polyacrylates, polystyrenes, and non-natural polyamides.

PECVD Siloxane and Fluorine‐Based Copolymer Thin Films

AbstractPlasma copolymerization is utilized to fabricate thin photonic films based on hexamethyldisiloxane (HMDSO, C6H18Si2O) and octafluorocyclobutane (OFCB, C4F8). The structure of the plasma copolymerized films is examined by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), and the optical properties including refractive index, n, and extinction coefficient, k, are determined by spectroscopic ellipsometry. The refractive indices, which range from 1.38 to 1.54, can be manipulated by adjusting the volume ratio of the two monomers, HMDSO and OFCB, during the polymerization. A nonlinear relationship between the refractive index and extinction coefficient with comonomer feed ratio is observed. A strong initial increase in both n and k as the amount of HMDSO is increased is attributed to significant defluorination of the resultant polymer films coupled with the formation of a C‐C rich crosslinked network. Once the network incorporates substantial amounts of Si‐C and Si‐O bonds, the refractive index starts to decrease slowly due to a lowering of the density. XPS and FTIR results confirm the changes in internal structure consistent with this mechanism.

Synthesis and characterization of water-soluble densely branched glycopolymers

In a one-pot synthesis, highly branched synthetic glycopolymers have been prepared using the ‘Strathclyde Methodology’ involving a protected galactose monomethacrylate, a branching comonomer (ethylene glycol dimethacrylate or divinylbenzene) and a chain transfer agent (dodecanethiol) with 2,2′-azo-bis-isobutyronitrile as the source of radicals. Branching was confirmed via MALS/SEC and 1H NMR spectroscopy. One attractive feature of the methodology employed is that in a single-step procedure highly branched polymers with molar masses over a range of two orders of magnitude were obtained by fine-tuning the composition of comonomer and chain transfer agent mole feed ratio. Deprotection of the isopropylidene galactose functionalities on the polymers was achieved, leading to water-soluble and potentially bio-compatible synthetic glycopolymers with branched main chain architecture.

Processing, Mechanical Property Development and <i>In Vitro </i>Hydrolytic Degradation Studies of a Poly(L-Lactide-<i>co</i>-ε-Caprolactone) Monofilament Fibre for Potential Use as an Absorbable Surgical Suture

The bulk ring-opening copolymerisation of L-lactide (LL) and ε-caprolactone (CL) with an initial comonomer feed ratio of LL:CL = 75:25 mol % was carried out using stannous acetate as the initiator at 120 oC for 48 hrs. The copolymer was characterised by GPC, DSC and TGA. Due to its ability to biodegrade in the human body, this type of copolymer has potential for use as an absorbable surgical suture. The copolymer obtained was melt spun at 153 oC using a small-scale melt-spinning apparatus and extruded into ice-cooled water to produce an as-spun monofilament fibre which was largely if not completely amorphous. Alternate off-line hot-drawing and annealing (3 cycles) was carried out in order to develop the fibre’s oriented semi-crystalline morphology. To complete the processing operation, thermal treatment was necessary to stabilize the fibre morphology. It was found that fixed annealing at 60 oC followed by free annealing at 60 oC stabilized the fibre morphology as a result of molecular relaxation. In vitro hydrolytic degradation studied in a phosphate buffer saline (PBS) solution of pH 7.4 at 37.0 ± 0.1 oC indicated that, after 6 weeks immersion in the buffer, the fibre’s tensile strength decreased by approximately 50% whereas a commercial ‘PDS’ suture of similar size lost its strength completely after only 4 weeks.

Precipitation Polymerization of 2-Methylene-1,3-dioxepane in Supercritical Carbon Dioxide

Free radical homopolymerization experiments were conducted with 2-methylene-1,3-dioxepane in supercritical carbon dioxide (scCO2) using a heterogeneous precipitation polymerization method and AIBN as the initiator. We also synthesized copolymers of 2-methylene-1,3-dioxepane with N-vinyl-2-pyrrolidone. The influence of comonomer feed ratios on the yield, glass transition temperature (Tg) and copolymer composition was investigated. The copolymers produced were characterized by 1H NMR, FT-IR spectroscopy and DSC. Reactivity ratios of comonomer in the initial step of the precipitation copolymerization process were estimated from copolymer composition analysis. In addition, we investigated the effect of reaction temperature on the reactivity ratios and determined that the reactivity ratios slightly increased and that MDOP had a larger deviation of reactivity ratio than that of NVP with the increased temperature. And the fine sub-micron sized copolymer particles containing with various comonomer ratios were prepared by aerosol solvent extraction system (ASES).

Copolymerization of tetracyclododecene or norbornene with styrene in the presence of Ni(II) complex/MAO catalytic system: First example for transition metal catalyzed copolymerization of tetracyclododecene with styrene

AbstractThe first example for transition metal catalyzed copolymerization of tetracyclododecene (TD) with styrene as well as of norbornene (NB) with styrene was achieved by the use of nickel(II) complex in the presence of MAO. High cyclic olefin contents of these copolymers were showed by 1H NMR measurements. Their GPC curves are all unimodal and Mw/Mn ratio of both homo‐ and copolymer samples are rather narrow value. These results show that these homo‐ and copolymerization take place at a single active site. The cyclic olefin content in these copolymers could be changed by changing the comonomer feed ratio. TD/styrene copolymers showed higher Tg value than that for NB/styrene copolymers and the Tg value were increases with an increase of TD content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

AIBN initiated free radical homopolymerization of N-(1-naphthyl)maleimide and copolymerization with MMA : synthesis and characterization

Free radical homopolymerization of N-(1-naphthyl)maleimide (NMI) and copolymerization with MMA were performed in THF at 65 °C with AIBN as the initiator. Nine copolymer samples were prepared using different feed ratios of comonomers. The prepared polymer sample have been characterized by solubility test, intrinsic viscosity, FT-IR and 1 H NMR spectral analysis. The thermal properties have been studied by thermo-gravimetric analysis.

Enzymatic Copolymerization to Hybrid Glycosaminoglycans: A Novel Strategy for Intramolecular Hybridization of Polysaccharides

Hybrid glycosaminoglycans (GAGs) having an intramolecularly hybridized structure of hyaluronan-chondroitin (3a) and hyaluronan-chondroitin 4-sulfate (3b) have been synthesized via enzymatic copolymerization catalyzed by hyaluronidase (HAase). N-Acetylhyalobiuronate (GlcAbeta(1-->3)GlcNAc)-derived oxazoline (1) was copolymerized with N-acetylchondrosine (GlcAbeta(1-->3)GalNAc)-derived oxazoline (2a) by HAase catalysis at pH 7.5 and 30 degrees C, giving rise to copolymer 3a with Mn 7.4 x 103 in a 50% yield. Also, HAase-catalyzed copolymerization of monomer 1 with N-acetylchondrosine oxazoline having a sulfate group at C4 on GalNAc (2b) was carried out to produce copolymer 3b with Mn 1.4 x 104 in a 60% yield. The copolymer compositions were controllable by varying the comonomer feed ratio. These hybrid GAGs were successfully digested by the catalysis of hyaluronan lyase, clearly exhibiting that the products are not a blend of different homopolymers but an intramolecularly hybridized GAG.

Free Radical Copolymerization of Methyl Methacrylate and Styrene with N-(4-Carboxyphenyl)maleimide

The free radical copolymerization of methyl methacrylate (MMA) or styrene (St) with N-(4-carboxyphenyl)maleimide (CPMI) was carried with AIBN as an initiator in THF solvent at 80°C. A series of copolymers of MMA and St with CPMI were prepared using different feed ratios of comonomers. The values of monomer reactivity ratios (r1, r2) determined by Fineman-Ross and Kelen-Tudos methods are 0.26 and 2.51 in the CPMI/MMA system and 0.08 and 0.22 in the CPMI/St system. Alfrey–Price Q-e values for CPMI were calculated as Q = 1.05 and e = 0.41 in the CPMI/MMA system and Q = 1.21 and e = 0.91 in the CPMI/St system. The polymer samples have been characterized by solubility tests, intrinsic viscosity measurements, FT-IR and 1H-NMR spectral analysis, and thermo-gravimetric analysis. It was found that the initial and final decomposition temperatures increased with increasing the amount of CPMI in the copolymer. The integral procedural decomposition temperature and energy of activation of thermal degradation have also been reported.

Hyaluronidase-Catalyzed Copolymerization for the Single-Step Synthesis of Functionalized Hyaluronan Derivatives

Hyaluronidase-catalyzed copolymerization was carried out with monomer combinations of 2-methyl (1a)/2-vinyl (1b), 2-methyl (1a)/2-ethyl (1c), 2-methyl (1a)/2-n-propyl (1d), and 2-vinyl (1b)/2-ethyl (1c) oxazoline derivatives of hyalobiuronate [GlcAbeta(1-->3)GlcN]. All copolymerization reactions proceeded successfully in a regio and stereoselective manner, giving rise to hyaluronan derivatives bearing different N-acyl groups at the C2 position of the glucosamine unit in the polymer chain. The composition of the N-acyl groups was controlled by varying the comonomer feed ratio. The copolymerization mechanism was also discussed.

Copolymerization of Methyl Methacrylate, Ethyl Acrylate, and Butyl Acrylate with N-2-Anisylmaleimide and Characterization of the Copolymers

The free radical copolymerizations of methyl methacrylate (MMA), ethyl acrylate (EA), and butyl acrylate (BA) with N-2-Anisylmaleimide (AMI), initiated by AIBN, were performed in THF solvent at 65°C. A series of copolymers of AMI-MMA, AMI-EA, and AMI-BA were prepared using different feed ratios of comonomers. The polymer samples have been characterized by solubility tests, intrinsic viscosity measurements, FT-IR, and 1H-NMR spectral analysis, and thermo-gravimetric analysis. The values of monomer reactivity ratios r1 and r2 determined by Fineman-Ross and Kelen-Tudos methods are 0.43 and 0.42 in AMI/MMA, 0.72 and 0.62 in AMI/EA and 0.76 and 0.72 in AMI/BA systems. Alfrey-Price Q-e values for AMI are Q = 3.13 and e = 1.71 in AMI/MMA, Q = 1.10 and e = 1.46 in AMI/EA and Q = 1.02 and e = 1.63 in AMI/BA systems. It was found that the initial and final decomposition temperature increased with increasing the component of AMI in the copolymer.