The radical polymerization of multivinyl monomers usually provides crosslinking polymers. It is a significant challenge how to control the structure of the polymers and to obtain soluble polymers in ...a high yield. In this work, the radical branching polymerizations of two asymmetrical divinyl monomers, allyl methacrylate (AMA) and furfuryl methacrylate (FMA), were investigated in detail. Both of the reactivity of the bonds and the weak transfer of isopropyl alcohol (IPA) were used to control the development of branching polymerizations and avoid gelation, without any other additives. As a result, the soluble branched PAMAs and PFMAs with extremely high molecular weights (106∼107) were successfully obtained. The branching factor (g’) of PAMA is very low (0.01–0.02), and that of PFMA is the higher (about 0.3) due to the weaker reactivity of furfuryl groups. Comparing with the results of using thiol chain transfer agent, the chain transfer of IPA had no obvious influence on the chain propagation at the early stage of the polymerizations, but could delay the gelation successfully at the later stage. Furthermore, the development of the branching structure could be studied in detail on the branching factor and rms radius since the gelation process was extended from several minutes to several hours.
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•Free radical homopolymerization of asymmetrical divinyl monomers without gelation.•Branched polymers with the high yield, molecular weight and low viscosity (branching factor).•Simple system, rapid polymerization and convenient controlling to polymerization.
Foamed silicone rubber was prepared by mixing 45% vinyl silicone oil (Base), Karstedt platinum catalyst (Cata), and hydrogenated silicone oil (SiH) and the resulting material was subjected to ...secondary vulcanization, which led to its performance requirements. Vinyl silicone oil and hydrogenated silicone oil underwent an addition reaction under the action of a platinum catalyst to form an elastomer with a cross-linked network structure. The results showed that by increasing the content of hydrogenated silicone oil in the formulation, the elongation at break of the foamed silicone gel material decreased but the tensile strength increased. When the content of hydrogenated silicone oil in the formulation decreased, the elongation at break of the foamed silicone material increased. When the content of Karstedt catalyst in the formulation increased, the formation time of the reaction gel was greatly shortened, and the cell structure tended to be dense but delicate. When the proportion of vinyl silicone oil in the formulation increased, the elongation at break of the foamed, molded silicone rubber increased. However, the elastic modulus decreased, and the thermal stability improved. Finally, a more suitable formulation of
V
Base
:
V
Cata
:
V
SiH
= 32:1:2 was obtained, which showed a tear resistance of 5.52 KN/m, ductility of 133%, and limiting oxygen index of 26 with a stability temperature of 346.8 °C when the thermal mass loss reached 95%.
Here, a new type of anionic hybrid copolymerization is exploited via the concurrent oxa‐Michael addition of ethylene glycol and neopentyl glycol diacrylate and the ring‐opening polymerization of ...ε‐caprolactone. The hybrid copolymerization process and the resulting copolymers are characterized using nuclear magnetic resonance, size exclusion chromatography, differential scanning calorimetry measurements, and thermogravimetric analysis. The results show that the hybrid copolymerization can proceed smoothly under mild reaction conditions and that the synthesized copolymer contains ester and ether structures in the backbone, possibly endowing the polymers with good hydrophilicity and degradability. More importantly, the composition of the synthesized polymer can be easily adjusted by changing the monomer feed ratio, and the chain crystallization is significantly reduced due to the random copolymeric structure. This hybrid copolymerization reaction provides a new method for synthesizing degradable functional copolymers from commercially available materials. Hence, this polymerization is important not only in polymer chemistry but also in environmental and biomedical engineering.
A new type of anionic hybrid copolymerization via the concurrent oxa‐Michael addition of a diacrylate and a diol and a ring‐opening polymerization of a lactone is reported. This hybrid copolymerization can be carried out under mild reaction conditions with excellent monomer conversions. The synthesized copolymer contains ester and ether structures in the backbone, and might give the polymers good hydrophilicity and degradability.
An approach to branched vinyl polymers through radical polymerization in the presence of 3-mercaptohexyl methacrylate (MHM) as the chain transfer monomer is reported in this paper. In the case of ...polymerization at styrene100–MHM5.0–AIBN2.0, the molecular weight increased with conversion and reached a value of >7.3 × 105 g/mol at 99% conversion; in addition, the Zimm branching factor, g′, was less than 1 and decreased with conversion, when the formation of the branched chain and development of branching was supposed. The bridging units in the obtained polymer, generating from MHM, were cleaved to yield the primary chains. These results have confirmed the formation of branched polymers. Moreover, this study successful prepared branched poly(methyl methacrylate) and poly(vinyl acetate). This methodology proposes good prospects for scaling-up and thereby offers a wide range of branched vinyl polymers at low cost.
A novel well-defined linear poly(ε-caprolactone) (P1) containing terminal azobenzene and ethyne groups was successfully synthesized through tin-catalyzed ring-opening polymerization of ε-caprolactone ...in the presence of N,N′-bis(2-hydroxyethyl)-4-(3-ethynylphenylazo)aniline (BHA) in bulk. Subsequent reactions allowed the synthesis of the corresponding bromoester end-functionalized polymer (P2), which was converted into AB2 type polymer (P3) containing terminal azide groups with NaN3. Consequently, hyperbranched poly(ε-caprolactone) (HPCL) was prepared with AB2 macromonomer (P3) by “click” chemistry under the catalysis of CuSO4·5H2O/sodium ascorbate/H2O. The structure of the resultant HPCL was characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (1H-NMR), ultraviolet-visible (UV-Vis) spectroscopy and fourier transform infrared spectroscopy (FT-IR). Thermal and crystallization properties of P1 and HPCL were further studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarised optical microscopy (POM). These results indicated that the crystallinity of HPCL was slightly lower than that of P1 due to the hyperbranched structure of HPCL. Additionally, the photo-induced trans-cis isomerization behaviors of BHA, P1 and HPCL containing terminal azobenzene were investigated in chloroform solution, and the photoisomerization rate constant (kexp) of small molecule (BHA) was nearly three times faster than that of polymers P1 and HPCL, which was due to the sterically hindering effect of the polymer-chain configuration.
The development of networks and structural heterogeneity in the atom transfer radical polymerization (ATRP) of dimethacrylates was studied. The structural and kinetic evolutions during the ...polymerization were followed using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and extraction/swelling measurement. The reversible activation/deactivation equilibrium between growing radical and dormant species slowed down the polymerization process, giving rise to sufficient chain relaxation and diffusion of reactive species, which favored the formation of homogeneous networks. Compared to the networks prepared by conventional free radical polymerization that favored microgel formation, the ATRP products were more homogeneous, suggested by narrower peak width of the tanδ curve. It was also found that crosslinking density and degree of structural heterogeneity of the ATRP products increased with vinyl conversion. The loss of the living feature at high conversions did not further increase the structural heterogeneity. The ATRP of dimethacrylates with longer spacer yielded more homogeneous networks with lower crosslinking density and lower glass transition temperature.
Novel hyperbranched copolymers were prepared by the atom transfer radical copolymerization of N-(4-α-bromobutyryloxy phenyl) maleimide (BBPMI) with styrene in 1-methyl-2-pyrrolidone (NMP) using the ...complex of CuBr/2,2′-bipyridine as catalyst. The copolymerization behavior was investigated by comparison of the conversion of double bond of BBPMI determined by 1H NMR with that of styrene. The hyperbranched structure of resulting copolymers was verified by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS). The influences of dosage of catalyst and monomer ratio on the polymerization rate and structure of the resulting polymers were also investigated. The glass transition temperature of the resulting hyperbranched copolymer increases with increasing mole fraction of BBPMI, fBBPMI. The resulting copolymers exhibit improved solubility in organic solvents; however, they show lower thermal stabilities than their linear analogues.
Branching atom transfer radical polymerization (ATRP) of styrene and acrylonitrile was attempted in the presence of divinylbenzene targeting toward soluble branched copolymer. The kinetics and the ...development of branching with monomer conversion were studied in detail. Gas chromatography (GC), gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), proton nuclear magnetic resonance (1H NMR) spectroscopy and intrinsic viscosity determination were used to monitor the polymerization process and characterize the obtained copolymer. Analysis of conversion of reactants, the growth manner of molecular weight with monomer conversion and GPC traces proved that the primary chains with low polydispersity formed mainly at the early stage and then were linked in a statistical manner to start the branching at the middle or late stage. The more the branching agent was used, the earlier the branching occurred, and too much higher level of branching agent resulted in gelation. For the selected ratio of t-BBiB/DVB/St/AN=1/0.9/15/15, with monomer conversion less than 40%, primary chains with low polydispersity formed from the polymerization of St, AN and DVB, and only a part of the primary chains contained pendent vinyl group. When monomer conversion was up to 40%, the pendent vinyl groups participated in polymerization, resulting in the linking of the primary chains statistically to start the branching. The branching became significant at monomer conversion up to 50%, giving rise to a steep increase in molecular weight and width in molecular weight distribution. As the polymerization proceeded, the polymer composition gradually approached the feed composition, identifying the obtained branched copolymer provided some gradients are in its primary chains. Finally, branched copolymer bearing about six primary chains was prepared at monomer conversion near to 80%, its absolute weight average molecular weight was about 8.87×104.
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