Chao Gao

Fluorescent polymer made from chemical modification of poly(styrene-co-maleic anhydride)

Abstract Poly(styrene-co-maleic anhydride) (SMA) was modified by commercially available fluorescent dye, 4-amino-N-(2,4-dimethylphenyl)-1,8-naphthalimide, to prepare fluorescent poly(styrene-co-maleimide) (SMI). FT-IR, UV–Vis and fluorescent spectra of this polymer were investigated. The polymer can emit strong yellow–green fluorescence (around 510 nm) and its thermal stability and solubility were improved. The number-averaged molecular weight (Mn) measured by GPC was about 1.8×105 relative to the polystyrene standard and the molecular weight distribution was 1.86. The glass transition temperature (Tg) determined by differential scanning calorimeter (DSC) was 150.8xa0°C, and 17xa0°C higher than the Tg (133.7xa0°C) of SMA. The influences of solvent, concentration and quencher on the fluorescent behaviors of SMI are discussed too.

Self-association of hyperbranched poly(sulfone-amine) in water: studies with pyrene-fluorescence probe and fluorescence label

Abstract Both pyrene-fluorescence probe and fluorescence label techniques are used to investigate the association behaviors of hyperbranched poly(sulfone-amine) (HPSA) in aqueous solution. In the presence of HPSA, excimer emission peak evidently appeared, while no excimer peak was observed in the emission spectra in the absence of HPSA. The excitation spectrum monitored at excimer emission red shifts by about 38–40xa0nm compared to that monitored at monomer emission, which shows that the excimer is formed by preassociated pyrene chromophores. In the same concentration of pyrene, monomer emission of pyrene decreases but excimer emission increases with increasing the concentration of HPSA; the ratio of excimer-to-monomer emission intensity (IE/IM) gradually increases, reaches a critical point at 5–7xa0g/l, and sharply increases with the concentration. Pyrene-labeled hyperbranched poly(sulfone-amine) (Py-HPSA) was synthesized from 4-(1-Pyrene)butyroyl chloride and HPSA. The monomer emission and excimer emission of Py-HPSA show the concentration-quenching effect, while IE/IM increases monotonously, approaches a critical point, and then suddenly increases with increasing the concentration of Py-HPSA. Influences of acidity and solvents on the fluorescence emission were studied. In high concentrations of hyperbranched polymer, pH and DMSO significantly influence the emission of pyrene, and excimer peak disappears at 72% of DMSO fraction.

Preparation of water-soluble hyperbranched poly(sulfone-amine)s by polyaddition of N-ethylethylenediamine to divinyl sulfone

Abstract The new approach for synthesis of hyperbranched polymers from commercially available A 2 and BB′ 2 type monomers has been further developed. Water-soluble hyperbranched poly(sulfone-amine)s with multiple amino end groups were prepared by direct polyaddition of divinyl sulfone (DV, A 2 ) to N -ethylethylenediamine (NDA, BB′ 2 ). Effects of reaction conditions such as the feed ratio and solvents on the polymerization have been investigated. When the feed ratio of DV to NDA was equal to 1, no gelation occurred during the polymerization in water or organic solvents. Similarly, when the feed ratio of DV to AP was equal to 3/2, no insoluble or cross-linked material was observed in chloroform or other organic solvents such as N , N -dimethylforamide, N , N -dimethylacetamide and N -methyl-2-pyrrolidone. Interestingly, when water was used as solvent, the reaction mixture got turbid within 15–20xa0min and gelation occurred within 12–15xa0h. The turbid mixture formed during initial stage becomes a transparent solution in aqueous acid, which was coined as ‘pseudo-gelation’. The solubility of the resulting polymer in water is as high as 1.68xa0g/ml. The degree of branching (DB) of all the resulting hyperbranched polymers is higher than 50% and the highest one is 70.9%. The reaction mechanism is presented and demonstrated with FTIR, HPLC and MS. During polymerization, secondary amino groups of NDA react rapidly with vinyl groups of DV within 12xa0s dominantly generating dimers which can be regarded as a new AB′ 2 type monomer. Further polymerization of the new monomers leads to hyperbranched poly(sulfone-amine)s.

Hyperbranched Polymers Made from A2- and BB′2 -Type Monomers, 3. Polyaddition ofN-Methyl-1,3-propanediamine to Divinyl Sulfone

The new approach to the synthesis of hyperbranched polymers from commercially available A 2 - and BB 2 -type monomer has been developed further. In this work, hyperbranched poly(sulfone amine)s with multiple amino end groups were prepared by direct polyaddition of N-methyl-1,3-propanediamine (NPA, BB 2 ) to divinyl sulfone (DV, A 2 ). The polymerization mechanism is presented and demonstrated with FT-IR, HPLC, and MS. During the reaction, the secondary amino groups of NPA react with the vinyl groups of DV within 12 s, generating dimers that can be regarded as new AB 2 -type monomers. Further polymerization of the new monomers leads to hyperbranched poly(sulfone amine)s. The influence of the reaction conditions, such as the feed ratio and solvents, on the polymerization has been investigated. When the molar feed ratio of DV to NPA is equal to 1 (A/B/B = 2/1/2), no crosslinking is observed in water or organic solvents. When the feed ratio of DV to NPA is equal to 3/2 (A/B/B = 3/1/2), no gelation occurs in chloroform or other organic solvents, such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone. Interestingly, when the polymerization was carried out in water with a feed ratio of 3/2, the reaction mixture got turbid within 20-30 min and gelation occurred with 15-20 h.

Hyperbranched polymers made from A2, B2 and BB′2 type monomers, 2. Preparation of hyperbranched copoly(sulfone-amine)s by polyaddition of N-ethylethylenediamine and piperazine to divinylsulfone

Abstract The new approach for preparation of hyperbranched polymers from commercially available A 2 and BB′ 2 type monomers was further extended to synthesize hyperbranched copolymers. In this work, hyperbranched copoly(sulfone-amine)s were prepared by polyaddition of piperazine (B 2 ) and N -ethylethylenediamine (BB′ 2 ) to divinylsulfone (A 2 ). The polymerization mechanism was investigated with FTIR and LC-MSD. During the copolymerization, secondary-amino groups of piperazine and N -ethylethylenediamine react rapidly with vinyl groups of divinylsulfone within 50xa0s, and then the residual vinyl groups react with primary-amino groups resulting in hyperbranched copoly(sulfone-amine)s. The crystallization behaviors of the resulting polymers were characterized with DSC and X-ray diffraction. When the initial mole ratio of B 2 to BB′ 2 is equal to or higher than three, r ≥3, resulting copolymers are semi-crystalline, while those with r r =3 exhibit the highest melting temperature comparing with other semi-crystalline samples. The degree of branching of hyperbranched copolymers was determined by 1 H NMR.

Self‐Association and Degree of Branching: Fluorescence‐Probe Study of Hyperbranched Poly(sulfone‐amine)s in Aqueous Solution

Pyrene is used as a fluoresence probe to investigate the self-association behavior of poly(sulfone aminels with various degrees of branching (DB). The ratio of exeimer to monomer emission intensity increases graally with DB, passes through a critical point at a DB of about 35%, and then increases draamatically. The study reveals that the higher DB, the stronger the association.

Hyperbranched Copolymers Made from A2, B2 and BB′2 Type Monomers, 3. Comparison of Copoly(sulfone‐amine)s Containing Piperazine and 4,4′‐Trimethylenedipiperidine Units

Hyperbranched copoly(sulfone-amine)s with various lengths of linear segments between two branching units were synthesized by copolymerization of A2 type monomer with B2 and BB′2 type monomers without any catalysts. Herein, A2 is divinyl sulfone (DV); B2 is piperazine (PZ) or 4,4′-trimethylenedipiperidine (TMDP), and BB′2 is 1-(2-aminoethyl)piperazine (AP) or N-methyl-1,3-propanediamine (NPA). Analysis by FTIR and LC-MSD confirmed the polymerization path that has been presented in previous papers of this series. The rapid reaction of secondary-amino groups of BB′2 and B2 with vinyl groups of A2 results in the formation of the intermediate containing one reactive vinyl group and two active hydrogen atoms. Further polymerization of this AB′2 type intermediates gives hyperbranched copoly(sulfone-amine)s. The analysis of DSC showed that the resulting branched copolymers were semi-crystalline when the feed ratio of B2 to BB′2 was equal to or higher than two. Furthermore, double-melting endotherms were observed in the corresponding DSC curves of the sample with TMDP units, while only one melting peak was observed for the sample with PZ units. The degree of branching (DB) of the copolymers obtained increased with decreasing the feed ratio of B2 to BB′2 monomers.

Hyperbranched copolymers made from A2, B2 and BB′2type monomers (iv)

The new approach for synthesis of hyperbranched polymers from commercially available A2 and type monomers was extended to synthesize hyperbranched copolymers. In this work, hyperbranched copoly(sulfone-amine) was prepared by copolymerization of divinyl sulfone (A2) with 4,4′-trimethylenedipiperidine (B2) and N-ethylethylenediamine (BB’2). During the reaction, secondary-amino groups of B2 and BB’2 monomers react rapidly with vinyl groups of A2 monomers within 35 s, generating a type of intermediate containing one vinyl group and two reactive hydrogen atoms. Now the intermediates can be regarded as a new type monomer, which further polymerizes to form hyperbranched copoly(sulfone-amine). The polymerization mechanism was investigated with FTIR and LC-MSD. The degree of branching (DB) of hyperbranched copolymers increased with decreasing the ratio of 4, 4′-trimethylenedipiperidine to N-ethylethylenediamine, so DB can be controlled. When the initial mole ratio of B2 to BB′2was equal to or higher than four,r≥4, resulted copolymers were semi-crystalline, while copolymers withr3 were amorphous.