Preformed Copolymers Research Articles

Polymeric micelles of a copolymer composed of all-trans retinoic acid, methoxy-poly(ethylene glycol), and b-poly(N-(2 hydroxypropyl) methacrylamide) as a doxorubicin-delivery platform and for combination chemotherapy in breast cancer

Delivery of combination chemotherapeutic agents to the tumor via nanovesicles has the potential for superior tumor suppression and reduced toxicity. Herein, we prepare a block copolymer (mPH-RA) composed of methoxy-poly(ethylene glycol) (mPEG), b-poly(N-(2 hydroxypropyl) methacrylamide) (pHPMA), and all-trans retinoic acid (ATRA) by conjugating ATRA to the pre-formed copolymer, mPEG-b-pHPMA(mP-b-pH). Doxorubicin-loaded micelles, Dox@mP-b-pH, and Dox@mPH-RA were characterized by determining particle size, zeta potential, % DL, EE, Dox release, hemolysis study, and by DSC. The Dox@mPH-RA micelles (mPH-RA: Dox ratios of 10:0.5–2) displayed nano-size (36–45 nm), EE. 26–74%, and DL. 2.9–5.6%. Dox@mPH-RA micelles displayed the highest penetrability and cytotoxicity than free Dox and Dox@mP-b-pH micelles in breast cancer cell lines. Dox@mPH-RA exhibited the highest induction of apoptosis (94.1 ± 3%) than Dox (52.1 ± 4.5%), and Dox@mP-b-pH (81.7 ± 3%), and arrested cells in the highest population in G2 and S phase. Dox@mPH-RA increased the t1/2 and Cmax of Dox and demonstrated improved therapeutic efficacy and highest Dox distribution to the tumor. The Dox@mPH-RA increased the levels of apoptosis markers, caspase 3, 7, Ki-67, and caused the highest DNA fragmentation. The presence of RA improved the micelles' physicochemical properties, Dox-loading ability, and the therapeutic potential in Dox@mPH-RA via the combination therapeutic strategy.

Novel fluorinated compound for imparting sustainable functionalities to cellulose-containing substrates

Herein we present an intensive investigation into the application of a copolymer formed through iodine transfer copolymerization of vinylidene fluoride with 2,3,3,3-tetrafluoro-1-propene. The unique properties of the pre-formed copolymer advocate it for inducing sustainable, multi-functionalized cotton-based textiles. The application of the preformed copolymer is carried out via the treatment of the cotton and cotton/polyester blend fabrics with the copolymer. The improvement of the physico-mechanical properties as well as the encapsulation of the copolymer within the cotton structure alone and in combination with polyester were affected by the absence and presence of epichlorohydrin as a crosslinking agent. A system consisting of the fiber-copolymer-crosslinking agent may result in mechanical entrapping and deposition of the copolymer in the structure of cotton. They work together with encapsulation for sustainable fixation of the copolymer in the overall structure of the fabrics either 100% cotton or cotton/polyester blend fabric (50/50). The augmentation was barely significant in smoothness and elongation at break of fabrics treated with the copolymer along with the crosslinking agent. SEM discovered that the treated fabrics are covered with a deposited film with tiny particles that can penetrate the fabric. EDX analysis confirms the presence of both fluorine and iodine. Also found was a polymer coating based on fluorine and iodine deposition leading to a hydrophobic product. Values of WRA of the treated fabrics place them in easy-care category with marginal losses in tensile strength and with the certainty that the treated fabric acquires waterproof properties.

Preparation of Poly(MA-alt-α-olefin-C6, 8, 12, 18)/Silica Nanohybrids via in situ generated nanofillers for use as a dual function organonanofiller

Four types of copolymer-silica nanocomposites have been prepared via ring-opening grafting of γ-aminopropyltrimethoxysilane (APTS) as reactive coupling agent onto preformed copolymers of maleic anhydride (MA) with 1-hexene, 1-octene, 1-dodecene and 1-octadecene and in situ hydrolysis (polycondensation) of side-chain ethoxysilane groups and tetraethoxysilane as a precursor in the presence of HCl catalyst. The copolymers of MA with 1-hexene, 1-octene and 1-dodecene were synthesized by free radical polymerization and another MA copolymer with 1-octadecene was supplied commercially as matrix copolymer. Chemical/physical structures, thermal behavior and morphology investigations of the generated hybrids were performed by FTIR, 13C, 29Si-NMR, TGA, SEM and TEM analysis methods. Nano-level hybridization through covalent bonding (amidization) between the anhydride unit of copolymers and amine group of APTS was observed, and nano-silica networks (hydrolysis) were obtained through acid catalyzed co-polycondensation of TEOS and ethoxysilane fragments from both coupling agent and precursor. Agreeing with 29Si-NMR and TGA quantitative analysis results, the degree of hydrolysis of ethoxysilane groups varied from 51.0 to 60.9%, and the content of in situ generated silica particles was found to be around 70.7-75.7%. Thermal properties and thermal stability of the obtained hybrids were found to be enhanced with silica content. SEM analysis confirmed the formation of nanostructural hybrids with relatively fine distributed nanoparticles. TEM analyses of all the nanohybrids indicate the formation of spherical morphologies. These novel copolymer hybrids are expected to be a promising and efficient organonanofiller for the preparation of polymer nanocomposites with both dual functionality and compatibilizer effects. Poly(MA-alt-α-olefin)/silica nanohybrids were obtained by an in situ sol–gel process of TEOS via nano-level hybridization as promising and effective organo nano-fillers.

Micellization and demicellization of amphiphilic poly(vinyl acetate)-graft-poly(N-vinyl-pyrrolidone) graft copolymers in the presence of sodium dodecyl sulfate

The micellization of amphiphilic biocompatible poly(vinyl acetate)-graft-poly(N-vinyl-2-pyrrolidone) (PVAc-graft-PNVP) graft copolymers, characterized by a constant PVAc backbone and PNVP side chains of low grafting density as well as of variable chain lengths, reveals the formation of star-like micelles with, at 25°C, a partially “frozen-in” PVAc core and a PNVP corona. The interaction of these graft copolymers with sodium dodecyl sulfate (SDS) was examined on the one side by the so-called “in situ micellization” process consisting in the solubilization of the copolymer in SDS solutions of fixed concentrations and on the other side by the demicellization of preformed copolymer micelles by adding increasing amounts of SDS. In both cases the SDS concentration was kept below its critical micellar concentration (CMC) and the system was investigated by dynamic light scattering (DLS), nuclear magnetic spectroscopy (NMR) and cryogenic-temperature transmission electron microscopy (cryo-TEM). When increasing amounts of SDS are added to a micellar solution of graft copolymer, three regions are observed. At very low surfactant concentrations (region I), a slight decrease in the hydrodynamic radius is observed as a consequence of the copolymer-rich/surfactant complex formation. This complex, which is preferentially formed between SDS hydrocarbon chains and PVAc sequences by hydrophobic interactions, leads to a higher content of the “mobile PVAc”. By a further increase of the SDS concentration (region II), the copolymer micelles start to disintegrate and an abrupt particle size decrease was noticed. A complete demicellization occurs at even higher SDS concentrations where small surfactant-rich/copolymer complexes, as unimers, are predominately present in the system (region III).

Poly(N-isopropylacrylamide-co-hydroxyethylacrylamide) thermosensitive microspheres: The size of microgels dictates the pulsatile release mechanism

Poly(N-isopropylacrylamide-co-N-hydroxyethylacrylamide) (poly(NIPAAm-co-HEAAm)) was prepared as a new thermosensitive copolymer possessing a sharp phase transition around the human body temperature. The effect of the copolymer concentration on the lower critical solution temperature (LCST) was determined under physiological conditions by cloud point (CP) and differential scanning calorimetric (DSC) methods. Then, thermosensitive microspheres were prepared from preformed copolymers by chemical cross-linking of hydroxyl groups with glutaraldehyde at a temperature situated slightly below LCST of the copolymer solution. The volume phase transition temperature (VPTT) of corresponding cross-linked microspheres was determined from swelling degree-temperature curve. The microspheres were loaded with model drug indomethacin by the solvent evaporation method. The DSC analysis proved that the drug is molecularly dispersed in the polymer network. Finally, the influence of the microsphere size on drug release was investigated. It was established that microspheres with the diameter ranging between 5 and 60μm release the drug with almost the same rate below (in the swollen state) and above the VPTT (in the collapsed state). On the contrary, microspheres with the diameter ranging between 125 and 220μm release a significantly higher amount of indomethacin below than above the VPTT. This different behavior is enough to assure a pulsatile release mechanism when the temperature changes cyclically below and above the VPTT. However, both small and large microspheres release a large amount of the drug during the collapsing process.

Novel functional degradable block copolymers for the building of reactive micelles

Amphiphilic biocompatible copolymers are promising materials for the elaboration of nanosystems for drug delivery applications. This paper aims at reporting on the synthesis of new functional amphiphilic copolymers based on biocompatible and bioeliminable blocks. Poly(ethylene oxide) was selected as the hydrophilic block, whereas an aliphatic polyester, i.e. poly(ε-caprolactone), or a polycarbonate, i.e. poly(trimethylene carbonate), was chosen as the degradable hydrophobic block. In order to allow a post-functionalization of the micelles core, azide groups were introduced on the hydrophobic segment to provide reactivity towards functional alkyne derivatives by the copper azide–alkyne cycloaddition (CuAAC). For this purpose, a functional lactone, i.e. α-chloro-ε-caprolactone, was introduced during the polymerization of the hydrophobic block before being converted into azide on the preformed copolymer. Such reactivity of the block copolymers and their self-assemblies is of prime interest for drugs or fluorescent dyes grafting, or for the crosslinking of the micelle's core. The influence of the azides distribution along the degradable block on the micelles post-functionalization ability has been studied by using alkyne bearing fluorescent dyes as models for drugs. The hydrophilicity of the dye on the micelles post-functionalization efficiency has also been investigated.

Polyolefins/Poly(3‐hydroxybutyrate‐co‐hydroxyvalerate) blends compatibilization: Morphology, rheological, and mechanical properties

AbstractPolypropylene/poly(3‐hydroxybutyrate‐co‐hydroxyvalerate) blend (PHBV) and polyethylene/PHBV blend were prepared by twin screw extruder using preformed copolymer (EVOH‐g‐PHBV) as compatibilizer or with functional polyolefins that can react in situ with the PHBV phase to form POs‐g‐PHBV. Scanning electron microscopy shows that by using either EVOH‐g‐PHBV preformed copolymer or formed copolymers in situ both emulsify the phase interface and reduce the interfacial tension, which result in an enhancement on the mechanical properties of compatibilized blends. Enhancement is more or less pronounced depending on the used PO matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Heterograft copolymers via double click reactions using one‐pot technique

AbstractThe double click reactions (Cu catalyzed Huisgen and Diels–Alder reactions) were used as a new strategy for the preparation of well‐defined heterograft copolymers in one‐pot technique. The synthetic strategy to the various stages of this work is outlined: (i) preparing random copolymers of styrene (St) and p‐chloromethylstyrene (CMS) (which is a functionalizable monomer) via nitroxide mediated radical polymerization (NMP); (ii) attachment of anthracene functionality to the preformed copolymer by the o‐etherification procedure and then conversion of the remaining CH2Cl into azide functionality; (iii) by using double click reactions in one‐pot technique, maleimide end‐functionalized poly(methyl methacrylate) (PMMA‐MI) via atom transfer radical polymerization (ATRP) of MMA and alkyne end‐functionalized poly (ethylene glycol) (PEG‐alkyne) were introduced onto the copolymer bearing pendant anthryl and azide moieties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6969–6977, 2008

Effectiveness of Graft Synthetic Polymers in Preventing Biodeterioration of Cellulose‐Based Materials

AbstractSynthetic polymers have been occasionally applied to the consolidation and protection of paper and cellulose‐based textiles especially when traditional conservation methods were not sufficient to improve the mechanical resistance of the degraded artefacts. In this paper, the potential of the innovative technique of grafting polymerisation with synthetic polymers was investigated to prevent biodeterioration. Cotton, linen and Whatman paper were consolidated by a) coating Paraloid B72®, b) coating ethyl acrylate/methyl methacrylate (EA/MMA) preformed copolymer, and c) grafting onto cellulose chains EA and MMA monomers in the ratio 75/25. All the samples were artificially biodeteriorated to obtain biodegraded model samples of both consolidated and non‐consolidated substrates, according to the ASTM G21‐96(2002) “Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi”. The consolidating effect was examined evaluating the mechanical behaviour of the grafted and coated samples, before and after the artificial biodeterioration. In addition, SEM observations were applied to monitor both the grafting level and the biodeterioration of the samples. With the grafting of acrylic monomers, the mechanical strength of cellulose‐based textiles and paper was greatly improved, as well as the resistance to biological agents. Therefore, with regards to biodeterioration, the graft copolymer EA/MMA (75/25 wt) was proved to be a suitable method to help prevent possible deterioration of paper and textiles.

Reactively and physically compatibilized immiscible polymer blends: stability of the copolymer at the interface

AbstractThis paper reports on the interfacial behaviour of block and graft copolymers used as compatibilizers in immiscible polymer blends. A limited residence time of the copolymer at the interface has been shown in both reactive blending and blend compatibilization by preformed copolymers. Polystyrene (PS)/polyamide6 (PA6), polyphenylene oxide (PPO)/PA6 and polymethylmethacrylate (PMMA)/PA6 blends have been reactively compatibilized by a styrene‐maleic anhydride copolymer SMA. The extent of miscibility of SMA with PS, PPO and PMMA is a key criterion for the stability of the graft copolymer at the interface. For the first 10 to 15 minutes of mixing, the in situ formed copolymer is able to decrease the particle size of the dispersed phase and to prevent it from coalescencing. However, upon increasing mixing time, the copolymer leaves the interface which results in phase coalescence.In PS/LDPE blends compatibilized by preformed PS/hydrogenated polybutadiene (hPB) block copolymers, a tapered diblock stabilizes efficiently a co‐continuous two‐phase morphology, in contrast to a triblock copolymer that was unable to prevent phase coarsening during annealing at 180°C for 150 minutes.

Stability Properties of Thermoresponsive Poly(N-Isopropylacrylamide)-Trypsin Conjugates

Trypsin was covalently coupled to poly(N-isopropylacrylamide) (pNIPAAm), a thermoresponsive polymer, through reactive groups of N-acryloxysuccinimide (NAS), which were incorporated into the polymer and the enzyme, respectively, prior to immobilization. Higher activity was retained for the enzyme that was coupled to the preformed copolymer of NIPAAm-NAS (conjugate I) as compared to conjugate II prepared by the other method. The conjugated trypsin was found to be more resistant to heat treatment than the free enzyme. Just the physical presence of the polymer had no significant influence on the thermal stability of the free trypsin. The activity loss in the conjugated enzymes during repeated precipitation/dissolution cycles was more due to incomplete recovery than to inactivation by temperature during the precipitation step. Conjugate I exhibited significant retention of activity after storage in acetonitrile and DMF, and was also used for dipeptide synthesis in acetonitrile.

Characteristics of organic gas sensitivity in copolymer LB films

The use of preformed copolymers and their cross-linking have been attempted in order to improve the intrinsic fragility of monolayers and Langmuir-Blodgett (LB) films and to make their technological applications possible. It has been shown that an imidization followed by a polyion-complexation can stabilize the LB films against heat and solvents. And, when the polymer structure was property designed, concurrent removal of the alkyl tails together with imide formation could he accomplished. In this paper, the interface can be transferred onto solid substrates such as porous fluorocarbon membranes filter and quartz crystal microbalance (QCM). The properties of the monolayers and the LB films investigated by π- A isotherms, FT-IR, DSC, deposition ratio, QCM and SEM will be discussed. In addition, it was attempted to investigate the reaction of polymer LB films in the organic gas surrounding by the use of QCM.

Functionalization of montmorillonite by acrylamide polymers containing side‐chain ammonium cations

AbstractStable polyacrylamide (polyAA)–montmorillonite adducts were prepared by two distinct processes: (1) free radical copolymerization of AA with alkaline clay previously treated with 2‐(N‐methyl‐N,N‐diethyl ammonium iodide)ethylacrylate (QD1) and (2) direct interactions of alkaline montmorillonite with various preformed copolymers of AA with QD1. The structure of the adducts as determined by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X‐ray diffraction was shown to consist of AA macromolecules inserted between lamellar layers whose spacing was larger than in the polymer‐free clay. The polymer was strongly attached to the inorganic surfaces, probably due to cooperative formation of electrostatic bonding. The thermal stability of the organic polymers in the resulting complexes was substantially enhanced while the mobility of macromolecules decreased.

Förster energy transfer between Langmuir-Blodgett film layers in aqueous solution

The Förster energy transfer between chromophores in several different types of Langmuir-Blodgett (LB) films exposed to aqueous conditions was examined. The donor and acceptor chromophores were either contained in a monolayer of a preformed copolymer incorporating amphiphilic side chains and hydrophilic spacer groups (dansyldihexadecylamine as the donor and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate as the acceptor) or grafted to a monolayer of such a copolymer (anthracene as the donor and 7-nitrobenz-2-oxa-1,3-diazole as the acceptor). The monolayers containing donor or acceptor chromophores were separated by neutral spacer layers of cadmium arachidate or copolymer material. It was found that the unattached chromophores diffused through the LB films during the experimental procedure and for several days afterwards. LB films containing chromophores that were grafted to copolymer and copolymer material spacer layers possessed high translayer structural order. There was evidence, however, that indicated that the structure relaxed with time.

Langmuir-Blodgett films of preformed copolymers of N-alkylacrylamides with vinylcarbazole

Copolymers of N-dodecylacrylamide and N-octylacrylamide with N-vinylcarbazole give stable monolayers on pure water. The copolymer monolayers can be transfered onto solid supports successively using the Langmuir-Blodgett (LB) method. The photoinduced electron transfer from carbazole in the copolymer monolayer to a viologen acceptor in the adjacent monolayer at the same interface was studied using the emission quenching method. It is concluded that the carbazole chromophore can be incorporated into the polymer LB film as a comonomer of alkylacrylamides which have excellent monolayer formation ability. This method is useful for obtaining a photofunctional polymer LB film.