Fourth Monomer Research Articles

Water-soluble biodegradable polyesters with pH and ionic responsivity

The synthesis of novel water-soluble polymers with biodegradability is an effective way to mitigate their negative environmental impacts. In this study, semi-aromatic copolyester poly(butylene succinate-co-butylene terephthalate) (PBST) with exceptional biodegradability is used as the resin matrix. Anionic sodium 1–3-isophthalate-5-sulfonate (SIPA) is introduced as a fourth monomer to prepare random poly(butylene succinate-co-butylene terephthalate-co-butylene 5-sodiosulfoisophthalate) (PBSTS) copolyesters by melt copolymerization. The incorporation of ionic groups enhances the hydrophilicity and water absorption of the copolyesters, resulting in water-soluble materials that exhibit ionic and temperature responsivity. Furthermore, the ionized biodegradable copolyesters demonstrate distinct pH-dependent degradation, which is accelerated at pH = 5.5 and 8.5 but inhibited at pH = 7.2. Degradation assessments in simulated body fluids reveal that the PBSTS copolyesters exhibit significant degradation in gastric fluids at pH = 1.5 with minimal degradation in intestinal fluids at pH = 6.8 and in body fluids at pH = 7.0. This unique degradation performance highlights the potential of these materials for addressing the challenges associated with selective drug delivery and localized controlled release in the human body.

Enhanced degradability of novel PBATCL copolyester: Study on the performance in different environment and exploration of mechanism

To enhance the biodegradability of poly (butyleneadipate-co-terephthalate) (PBAT), ε-caprolactone (ε-CL) was introduced as a fourth monomer, resulting in poly (butyleneadipate/terephthalate-co-caprolactone) (PBATCL) with different adipic acid/terephthalic acid (A/T) ratios and CL contents. These polyesters maintained superior thermal stability and improved hydrophilicity compared to PBAT. Samples were placed under artificial conditions, including non-enzymatic and enzyme-containing phosphate-buffered saline, and two natural soil and oceanic environments for 180 days to investigate the material’s degradation behaviors. PBATCL exhibited poor non-enzymatic hydrolysis similar to that of PBAT, but dramatically improved degradability in the presence of enzymes and microorganisms. Therefore, the material can be quickly degraded in natural environment by adjusting the composition ratio. The degradation mechanism was further investigated from a chemical structure perspective via the two dimensions of water-soluble intermediates and the residual matrix, and we found that the content of adipic acid (AA) and CL contributed to degradability. The ester bond formed by AA and CL is susceptible to hydrolysis, while the CL introduction also promotes the ester bond reactivity between the aromatic segments. Furthermore, Cell Counting Kit-8 (CCK-8) experiments showed that the degradation products were non-toxic and harmless to organisms. These results lay the foundation for designing targeted biodegradable polymers and provide a reference for understanding thedegradation mechanism of such materials.

Synthesis of novel block polymers with unusual block sequences by methodology combining living anionic polymerization and designed linking chemistry

This article reviews the various developments of a new methodology combining the living anionic polymerization and a designed linking chemistry for the synthesis of block polymers using two, two of three, three, or four monomers with different reactivities. With this methodology, a number of well-defined triblock copolymers, triblock terpolymers, tetrablock quaterpolymers, and multiblock copolymers with alternating two segments have been successfully synthesized. The obtained polymers were all novel well-defined block polymers with unusual block sequences. More importantly, they are definitely inaccessible by the sequential polymerization using monomers with different reactivities. The monomers used in the synthesis were mainly styrene, 2-vinylpyridine, and methyl (or tert-butyl) methacrylate classified into three categories by their reactivities. In addition, 1,2-butylene oxide was used as the fourth monomer to synthesize the tetrablock quaterpolymers. There are also a number of other monomers classified into each of these categories, which can be readily replaced from the main monomers. By developing the methodology using these monomers, it becomes possible to synthesize a far more number of block polymers beyond our imagination. In practice, several synthetic feasibilities are described in each chapter. The key for this synthetic success is to suitably choose an α-phenylacrylate function used as the reaction site, capable of quantitatively linking with each of the living anionic polymers having a wide range of reactivity, which makes it possible to connect two different polymer segments difficult to access by the sequential polymerization. One more important issue is to employ the iterative linking process, which enables the successive synthesis of alternating multiblock copolymers of up to the decablock type and possibly with more blocks. Generality, versatility, and advantages of the proposed methodology have been demonstrated throughout the synthesis of the block polymers.

Synthesis and evaluation of a Tetra-copolymer for oil displacement

In this paper, acrylamide (AM), 2-acrylamide-2-methylpropane sulfonic acid (AMPS), diacetone acrylamide (DAAM) were used as the basic monomers, and N, N-dimethylacrylamide (DMAM) with hydrophobic groups was introduced as the fourth monomer. The AM/DAAM/AMPS/DMAM Tetra-copolymer was synthesized by aqueous solution polymerization using the redox system of potassium persulfate and sodium bisulfite as initiator. The synthesis conditions of the copolymer were optimized by orthogonal test with five factors and four levels. The structure of the copolymer was characterized by FTIR and the thermal stability of the copolymer was analyzed by TGA. Relevant experimental results showed that the viscosity retention rate of the copolymer was higher than that of HPAM at the same temperature, salinity and shear rate. The viscosity retention rate of the copolymer was 72.7% after aging 30 days at 90 °C in the solution with 15000 mg/L the total salinity. The oil displacement experiment showed that the average recovery of the polymer flooding with 1000 mg/L prepared copolymer was as high as 10.8%.

Tailoring the degradation rates of thermally responsive hydrogels designed for soft tissue injection by varying the autocatalytic potential

The ability to modulate the degradation properties of biomaterials such as thermally responsive hydrogels is desirable when exploring new therapeutic strategies that rely on the temporary presence of a placed scaffold or gel. Here we report a method of manipulating the absorption rate of a poly(N-isopropylacrylamide) ((poly(NIPAAm)) based hydrogel across a wide range (from 1 d to 5 mo) by small alterations in the composition. Relying upon the autocatalytic effect, the degradation of poly(NIPAAm-co-HEMA-co-MAPLA), (HEMA = 2-hydroxyethyl methacrylate; MAPLA = methacrylate-polylactide) was greatly accelerated by adding a fourth monomer methacrylic acid (MAA) at no more than 2 mol% to obtain poly(NIPAAm-co-HEMA-co-MAPLA-co-MAA) (pNHMMj) where j reflects the MAA molar % in the reactant mixture. MAA residue introduction decreased the pH inside the hydrogels and in surrounding buffered solutions. Accelerated degradation positively correlated with MAA content in pNHMMj polymers, putatively by the accelerated cleavage of MAPLA residues to raise the transition temperature of the polymer above body temperature. Physical properties including thermal transition behavior and initial mechanical strength did not vary significantly with MAA content. A rat hindlimb injection model generally reflected the in vitro observation that higher MAA content resulted in more rapid degradation and cellular infiltration. The strategy of tuning the degradation of thermally responsive hydrogels where degradation or solubilization is determined by their polyester components might be applied to other tissue engineering and regenerative medicine applications where designed biomaterial degradation behavior is needed.

Structures and properties of easily dyeable copolyesters and their fibers respectively modified by three kinds of diols

Three kinds of modified poly(ethylene terephthalate) copolyesters were synthesized, using sodium-5-sulfo-bis-(hydroxyethyl)-isophthalate as the third monomer, 1,3-propanediol (PDO), 2-methyl-1,3-propanediol (MPD), and 2,2-dimethyl-1,3-propanediol (neopentyl glycol or NPG) as the fourth monomer, respectively. The copolyester fibers were also prepared by melt spinning and drawing processes. The effect of PDO, MPD, and NPG on the synthesis and spinning process was investigated, and the structures and properties of both copolyesters and the produced fibers were characterized. The results exhibited that the structural difference of PDO, MPD, and NPG played an important role in the synthesis and spinning process, and significantly affected the structures and properties of both copolyesters and the produced fibers, which thereby resulted in the difference in terms of dyeability improvement of copolyester fibers. The dyeing at boiling temperature under normal pressure experiments of copolyester fibers in both disperse dyebath and cationic dyebath revealed that incorporation of the fourth monomer could improve the dyeability of copolyester fiber, and copolyester fiber containing MPD unit had better dyeability due to a looser, more accessible structure when compared with the fiber containing PDO or NPG unit. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and Characterization of the Hydrophilic Copolyester

A series of hydrophilic copolyesters were prepared via copolymerization method with purified terephthalic acid (PTA), ethylene glycol (EG), 5-sodium suflo bis-(hydroxyethyl) isophthalate (SIPE) as the third monomer, and different content of polyols (FMA01) as the fourth monomer. The chemical structures of the hydrophilic copolyester were described by Fourier transform infrared spectroscopy(FTIR), and the thermal properties of the samples were studied by thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC). The hydrophilic properties of the samples were measured by contact angle(CA) measurements. Results showed that such modified copolymers had excellent hydrophilic properties. When SIPE reached 3mol% and FMA01 reached 0.8mol%, the copolyester film turned its wetting property to hydrophilic with water contact angle of 53.7°.

Structures and Properties of Modification Copolyester Fiber

This study investigated the structures and properties of cationic dyeable poly(ethylene terephthalate) (CDP) and easy cationic dyeable poly(ethylene terephthalate) (ECDP) by FTIR, X-ray diffraction, mechanical test, and DSC. The results showed that the FTIR spectrums of CDP and ester-type ECDP fibers were similar to the that of PET. It suggested that the adding of the third monomer and the fourth monomer had good compatible with the original structure unit of PET. the position of X-ray diffraction peak of CDP and ester-type ECDP were the same as which of PET, the third monomer and the fourth monomer did not pack into the original polyester unit cell but concentrated at the polyester crystalline surface and the amorphous regions.With adding the third monmome and the fourth monmomer, the initial modulus of the CDP and ester-type ECDP fibers became inferior. But the breaking elongation of them increased. The DSC suggested that The melting range of CDP and ECDP finished fiber were wider than that of PET fiber, but the melting point and crystallinity were less than them of PET fiber.

Thermal Properties of Ester-Type Easy Cationic Dyeable Poly(ethylene Terephthalate) (ECDP) Polymers

This study investigated the thermal properties of ester-type easy cationic dyeable poly(ethylene terephthalate) (ECDP) polymers using differential scanning calorimetry (DSC), therogravimetric analysis (TGA). The mass ratios of 5-sodium sulfo bis(-hydroxyethyl) isophthalate(SIPE) for ECDP polymers were 2.8%, 5.5%, 6.8%, respectively. The fourth monomers were diethylene glycol adipate (DGA), diethylene glycol succinate (DGS) and diethylene glycol subacate (DES) with different contents. The results suggested that the Tg of ester-type ECDP decreased with the increasing the molecule weight of the fourth monomer at fixed SIPE and fourth monomer contents. The Tch of ECDP polymer to be lower than that of the CDP polymer with the same SIPE content. And it decreased as SIPE and fourth monomer contents increased, it also decreased with the increasing of the molecule weight of the fourth monomer given the same SIPE content. The effect of the ester-type soft segments reduced the Tm of ECDP. The thermal stability of ECDP polymer was less than PET and CDP polymers, and it decreased with increasing SIPE content, but increased with the ester-type fourth monomer content increasing.

Crystal Structures of F420-dependent Glucose-6-phosphate Dehydrogenase FGD1 Involved in the Activation of the Anti-tuberculosis Drug Candidate PA-824 Reveal the Basis of Coenzyme and Substrate Binding

The modified flavin coenzyme F(420) is found in a restricted number of microorganisms. It is widely distributed in mycobacteria, however, where it is important in energy metabolism, and in Mycobacterium tuberculosis (Mtb) is implicated in redox processes related to non-replicating persistence. In Mtb, the F(420)-dependent glucose-6-phosphate dehydrogenase FGD1 provides reduced F(420) for the in vivo activation of the nitroimidazopyran prodrug PA-824, currently being developed for anti-tuberculosis therapy against both replicating and persistent bacteria. The structure of M. tuberculosis FGD1 has been determined by x-ray crystallography both in its apo state and in complex with F(420) and citrate at resolutions of 1.90 and 1.95 A(,) respectively. The structure reveals a highly specific F(420) binding mode, which is shared with several other F(420)-dependent enzymes. Citrate occupies the substrate binding pocket adjacent to F(420) and is shown to be a competitive inhibitor (IC(50) 43 microm). Modeling of the binding of the glucose 6-phosphate (G6P) substrate identifies a positively charged phosphate binding pocket and shows that G6P, like citrate, packs against the isoalloxazine moiety of F(420) and helps promote a butterfly bend conformation that facilitates F(420) reduction and catalysis.