For the preparation of thermoresponsive copolymers, for e.g., tissue engineering scaffolds or drug carriers, a precise control of the synthesis parameters to set the lower critical solution temperature (LCST) is required. However, the correlations between molecular parameters and LCST are partially unknown and, furthermore, LCST is defined as an exact temperature, which oversimplifies the real situation. Here, random N-isopropylacrylamide (NIPAM)/dopamine methacrylamide (DMA) copolymers were prepared under a systematical variation of molecular weight and comonomer amount and their LCST in water studied by calorimetry, turbidimetry, and rheology. Structural information was deduced from observed transitions clarifying the contributions of molecular weight, comonomer content, end-group effect or polymerization degree on LCST, which were then statistically modeled. This proved that the LCST can be predicted through molecular structure and conditions of the solutions. While the hydrophobic DMA lowers the LCST especially the onset, polymerization degree has an important but smaller influence over all the whole LCST range.

The effect of the molecular weight on the lower critical solution temperature (LCST) has been discussed extensively, where LCST increased with molar mass, decreased or kept constant, which leads to confusion. This work is focused on the preparation of poly(N‐isopropyl acrylamide) homopolymers, obtained in a wide molecular weights range. The LCST behavior is analyzed by calorimetry and rheology, and a deep study of molecular features is carried out for a better knowledge of the influence of various parameters involved on LCST. Finally, the molecular weight trend is observed, and its influence on LCST is compared with the effect of other parameters as polymer concentration in water, end‐group effect, and tacticity. It is observed that other parameters such tacticity and end‐group effect will affect the LCST behavior over molecular weight, if this one is not high enough. Furthermore, the study of the LCST ranges will be a useful tool for analyzing the molecular weight trends. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1386–1393

Poly(N‐Isopropylacrylamide) has a broad potential range of biomedical applications owing to its lower critical solution temperature (LCST). This work tries to elucidate the real influence of several parameters on LCST by comparing homopolymers prepared by free radical polymerization and reversible addition–fragmentation chain transfer (RAFT) polymerization using conventional calorimetry, turbidimetry, and rheology as well as how three different methods can be used to detect the LCST. These methods are compared to gain a deeper understanding of the underlying processes and how they are related to molar mass and synthesis methods. The diverse interactions associated with the LCST transitions are more sensitive depending on the ratio defined between polymerization degrees and end‐group effects. Thus, the selection of a high sensitive method for LCST detection depends on the molecular features defined from the homopolymer. In addition, this work shows also the importance of the RAFT agent selected for the synthesis, which can modify substantially the LCST in comparison with other methods reported where the use of chemicals, complex processes, and costs considerably increase.

a broad range of applications. Additional functionalities and other features can be obtained through the preparation of composites, hybrid materials, or functionalizing the original polymers. Some of these approaches focused on obtaining new kinds of catalysts, which are soluble in water, ecofriendly, and recyclable.Such procedures usually require numerous steps, such as the polymerization of glycidyl methacrylate, which is preceded by amination of the epoxy group with diethanolamine. [1] The resulting triethanolamine-pendant ligand can react with cyclopentadienyltitanium(IV) trichloride and derivatives, allowing the incorporation of the organometallic complex. [1] The combination of some organometallic complexes with poly(N-isopropyl acrylamide) (PNIPAM) could extend the properties associated with its thermoresponsive behavior. It is well known that its lower critical solution temperature (LCST) is around body temperature and can also provide reversibility. [2] Some approximations to this work were previously performed by atomic transfer radical polymerization (ATRP) using catalytic systems based on Cu. [3][4][5][6] The use of living chain-growth radical polymerization combined with step step-growth polymerizationThe functionalization of different structures with organometallic complexes provides exciting properties in terms of applicability due to its ability to provide multiple benefits for catalysis and biomedicine as well as in other fields. This work reports the direct, facile functionalization of copolymers based on N-isopropylacrylamide and dopamine methacrylamide with bis(cyclopentadienyl)titanium (IV) dichloride (Cp 2 TiCl 2 , Cp = η 5 -C 5 H 5 ), which can offer an easy preparation method in comparison with other functionalization procedures. In addition, the lower critical solution temperature (LCST) is studied through aqueous solutions of new structures, which is affected by the presence of the metallocene moieties. UV-vis spectroscopy shows an average of the LCST-behavior in comparison with rheology that provides essential information about the changes of the phase transition temperature associated with the composition of the polymeric chains and their interactions with the medium. Then, the inclusion of an organometallic complex along the polymeric chain can partially modify the phase transition temperature due to the interactions promoted by the organometallic complex of surroundings over the polymeric sections free of comonomer content.