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In this present work, physical hydrogels were prepared by the reaction between pectin and bis (3-aminopropyl) amine (APA) using N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as catalysts. These pectin-graft-bis (3-aminopropyl) amine (pec-g-APA) copolymers exhibited the electrostatic induced sol-gel phase transition at the predetermined pH values. Sol-gel phase diagrams demonstrated both lower- and upper- phase boundaries, corresponding to sol-gel phase transition and gel-sol phase transition, respectively, upon varying pH of the system. The phase transition depended on the APA composition as well as the copolymer concentration so that the gelation can be manipulated. The hydrogels were non-cytotoxic and exhibited the potential use for controlled release of gentamicin. Also, the antimicrobial activity of released gentamicin remained unaffected by the hydrogels.

Meso-scale simulations have been widely used to probe aggregation caused by structural formation in macromolecular systems. However, the limitations of the long-length scale, resulting from its simulation box, cause difficulties in terms of morphological identification and insufficient classification. In this study, structural knowledge derived from meso-scale simulations based on parameters from atomistic simulations were analyzed in dissipative particle dynamic (DPD) simulations of PS-b-PI diblock copolymers. The radial distribution function and its Fourier-space counterpart or structure factor were proposed using principal component analysis (PCA) as key characteristics for morphological identification and classification. Disorder, discrete clusters, hexagonally packed cylinders, connected clusters, defected lamellae, lamellae and connected cylinders were effectively grouped.

In this present work, stimuli responsive polymers that can respond to the temperature and pH of the environment were prepared. A series of temperature responsive diblock copolymers based on poly(ethylene glycol) methyl ether (mPEG) and e-caprolactone (CL) were synthesized. Subsequently, the diblock copolymers were grafted onto chitosan, a pH responsive biopolymer. These chitosan-graft-(mPEG-block-PCL) (chitosan-g-(mPEG-b-PCL)) graft copolymers were structurally characterized by 1H NMR and FTIR and their sol-gel phase transitions were analyzed by the test tube inversion method as well as dynamic rheological measurements. These chitosan-g-(mPEG-b-PCL) graft copolymers demonstrated tunable temperature and pH responsive sol-gel phase transitions that correspond well with body temperature and pH of acidic tumor microenvironments. Gelation temperature (Tgel) decreased with increasing pH of the system, increasing PCL composition in the diblock copolymers, increasing solution concentration and decreasing grafting content of the diblock copolymers on chitosan. The graft copolymer hydrogels successfully showed the sustained release of both doxorubicin and curcumin for up to 2 weeks. The designed system was based on chitosan-g-(mPEG-b-PCL) graft copolymers, of which chitosan showed pH responsive properties and mPEG-b-PCL acted as a temperature sensitive moiety. In addition, mPEG and PCL are recognized as biocompatible polymers and chitosan has been engaged in various pharmaceutical research. Thus, this system could be considered an alternative choice for drug delivery applications.

Injectable hydrogels are alternative materials for drug and protein delivery in biomedical applications, which can potentially eliminate the need of surgical implantation in the treatment procedures. Prior to administration, such hydrogels, in a liquid state, must demonstrate good interactions with the incorporated molecules to maintain the sustain release of active agents and to avoid unappreciative burst release. The injectable hydrogels derived from BSA-pH/temperature responsive poly(amino urethane) conjugates have been reported to demonstrated good sustainability for delivery of lysozyme, both in vitro and in vivo. However, the interactions between such conjugates and the loading lysozyme were not fully understood. In this present work, we reported the binding interactions between the studied complex systems, BSA-pH/temperature responsive poly(amino urethane) conjugates (CONJ1 and CONJ2) and lysozyme. Fluorescence spectroscopy in a combination with thermodynamic analysis exhibited that the binding between the conjugates and lysozyme occurred through static quenching and the binding interactions in the complexes were mainly van der Waals forces and hydrogen bonds. The binding constants (KA) determined at 300, 308 and 318K of CONJ1 to lysozyme were 7.96×10(4), 6.45×10(4) and 3.20×10(4)M(-1), respectively and those of CONJ2 to lysozyme were 2.63×10(4), 2.53×10(4) and 1.19×10(4)M(-1), respectively. FTIR analysis showed that the complexes between the conjugates and lysozyme demonstrated sufficiently small deviation in the conformational structures from the native lysozyme. In addition, the morphology revealed by TEM and AFM imaging portrayed the behavior of complex formation in such a way that the conjugates, before complex formation, displayed the core-shell structures. After the complex formation, a number of lysozyme particles were noticeably entrapped as if they penetrated into the preformed core-shell conjugates.

Polylactide (PL) finds its use in a wide variety of applications ranging from medical devices to engineering plastics. However, the use of PL is limited to certain applications due to its brittle characteristic and low heat distortion temperature, which indicate its poor mechanical and thermal properties, respectively. This present work demonstrated the toughening of PL by stereocomplexation adopting poly( d -lactide)–poly(ethylene glycol)–poly( d -lactide) (PDL–PEG–PDL) copolymers with various PDL segment length. The DSC results showed that the complete stereocomplexation was reached when 40 wt% copolymer was blended with poly( l -lactide) (PLL). In addition, the crystallization of PEG was interrupted and, thus, prohibited by either adding PDL or PLL in the system. AFM images showed that, for the first time, the stereocomplex crystallites (Sc-crystallites) formed by the enantiomer pairs were dispersed in a continuous amorphous phase of PL and the non-crystallizing PEG. The increase of PDL segment length in the copolymer leaded to the increase of the Sc-crystallite size, which, consequently, resulted in the increase of the tensile strength of the blended-films. Elongation at break of the films was found to rely on the determined amorphous area. To maximize the toughness of the films, the specific ratio of PDL and PEG segment length in the copolymer must be achieved to provide the optimum balance between Sc-crystallite size and % amorphous area.

Poly(amino urethane) (PAU) conjugated bovine serum albumin (BSA) hydrogels were prepared in a sequential step synthesis. The synthesis included preparation of PAUs, acrylation of the synthesized PAUs and conjugation of PAUs to BSA. The conjugation reaction was confirmed by Fourier transform infrared spectrometry (FT-IR) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The conjugate exhibited pH and temperature induced sol–gel phase transitions, facilitating the DOX-loaded conjugate solution to form gels at the physiological conditions. The release of DOX from the conjugate hydrogel proceeded without the initial burst and persisted over 5 weeks. The cytotoxicity results showed that the conjugate was non-cytotoxic, allowing uses of this material in bioapplications.

Albumin-conjugated pH and thermo responsive poly(amino urethane) multiblock copolymers are synthesized. The aqueous solution of the conjugate exhibits pH/temperature dependent sol-gel phase transitions that can be tuned by changing solution concentration and albumin composition. The gel window well covers the physiological condition allowing the flowing liquid to readily form the solid gel under the back of the Sprangue-Dawley (SD) rats. The release profile of lysozyme, as a model protein, shows that the conjugate hydrogel is able to effectively reduce the burst effect, in vivo, and maintain the sustained release of lysozyme over 4 and 2 weeks in the in vitro and in vivo experiments, respectively. Such conjugate hydrogel can be considered as a potential candidate for long-term delivery of proteins.

Copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) were prepared by partial hydrolysis of PMMA in bad solvent. These copolymers evidently have a blocky comonomer distribution –strands of predominantly MMA or MAA across the polymer– and show sharp transitions in aqueous solution upon pH change. Additionally, their hollow microcapsules show an exceptional and prolonged stability at acidic conditions (pH 2) and pH-triggered release at physiological conditions.

A novel heat-sealing performance is achieved by polyethylene (PE) nanocomposites reinforced by ethylene vinyl acetate (EVA) and montmorillonite (MMT). Appropriate nanocomposite design leads to hermetic seals with a general peelable/easy-open character across the broadest possible sealing temperature range. Observations of the fracture seal surfaces by infrared spectroscopy and electron microscopy reveal that this behavior originates from a synergistic effect of the EVA copolymer and the montmorillonite clay nanofiller. Namely, the combination of EVA-copolymers and MMT nanofillers provides sufficiently favorable interactions for nanocomposite formation and mechanical robustness, but weak enough interfacial adhesion to promote a general cohesive failure of the sealant at the EVA/MMT interfaces.

Albumin-conjugated pH and thermo responsive poly(amino urethane) multiblock copolymers are synthesized. The aqueous solution of the conjugate exhibits pH/temperature dependent sol-gel phase transitions that can be tuned by changing solution concentration and albumin composition. The gel window well covers the physiological condition allowing the flowing liquid to readily form the solid gel under the back of the Sprangue-Dawley (SD) rats. The release profile of lysozyme, as a model protein, shows that the conjugate hydrogel is able to effectively reduce the burst effect, in vivo, and maintain the sustained release of lysozyme over 4 and 2 weeks in the in vitro and in vivo experiments, respectively. Such conjugate hydrogel can be considered as a potential candidate for long-term delivery of proteins.

A novel heat-sealing performance is achieved by polyethylene (PE) nanocomposites reinforced by ethylene vinyl acetate (EVA) and montmorillonite (MMT). Appropriate nanocomposite design leads to hermetic seals with a general peelable/easy-open character across the broadest possible sealing temperature range. Observations of the fracture seal surfaces by infrared spectroscopy and electron microscopy reveal that this behavior originates from a synergistic effect of the EVA copolymer and the montmorillonite clay nanofiller. Namely, the combination of EVA-copolymers and MMT nanofillers provides sufficiently favorable interactions for nanocomposite formation and mechanical robustness, but weak enough interfacial adhesion to promote a general cohesive failure of the sealant at the EVA/MMT interfaces.