| Ethylenediamine modified poly-lactic acid (EMPLA) is a new biomedical material, there are the characters of good hydrophile and stabilization acid-alkalescence, it is known as a up-and-coming biomedical material in medical-engineering field. but, some troubles in physical-chemistry property aspects haven't been solved in the past. for example, molecular radius, graft ratio , the relation of these quantities and the biocompliable between graft ratio and cell. The application of clinic is affected by these unsolved question. So, the physical-chemistry properties of EMPLA were researched by gel permeation chromatography (GPC)-the eighteen angle laser light scattering detectors technology. At last, we researched the relation between graft ratio and cell growth. We obtained the following results and conclusions:[1] The dn/dc value is named as the differential refractive index increment, it reflect the degree of the solvent-solute with respect to a change in solute concentration,expressed in ml/g(this factor must be measured independently using DRI batch mode before experiment),we obtained the following result by analysis: the dn/dc value of PLA is 0.0536ml/g and EMPLA is 0.0515ml/g, the first one is higher than the last one, the result indicate the first is lower the last one in effect each other.[2] The second virial coefficient(A2) is a measure of the thermodynamic quality of the solvent for a given macromolecular polymer. It reflects the effect of the solvent and the solvent, the solvent and the solute each other.(the factor is measured by the eighteen angle laser light scattering detector in batch mode). The result is as follows: the A2 value of PLA is 4.980±0.999e-3 mol mL/g2 and EMPLA is 2.034±0.387e-3 mol mL/g2, Higher positive value of A2 is characteristic for better solvent.[3] The Signal to Noise ratio(S/N)is a concept in electroacoustics field, it is defined as the ratio between signal intensity and noise intensity. The inject loop affect the Signal to Noise ratio. Compared with 20μL and 500μL inject loop, the results showed the 500μL inject loop is better than the other. So we choose the 500μL inject loop as the inject choice in the experiment.[4] Compared with chloroform and tetrahydrofuran for the purpose of getting accord solvent, the result indicated the THF is better.[5] We researched the effect that the concentration is a important factor for molecular weight and graft ratio, optimized the analysis condition. Based on the design strategy of the experiment in different concentration condition, the result shows as follows: the molecular weight increase by the concentration increasing. The peak time don't change, usually, the time is twenty minutes or so. The molecular weight distribution don't change, either. The reliability degree of measuring the molecular weight and molecular weight distribution is the highest (reach to 97%) when the concentration is 3.0mg/ml. So we think 3.0mg/ml. as best concentration choice.[6] The flow speed was research by comparing with the reliability degree of measuring the molecular weight and molecular weight distribution under different conditions, the result is as follows: obviously, the peak time changed a lot with the flow speed changing. The time is shorter while the flow speed increases. But, the weight-average molecular weight, the number-average molecular weight, the z-average molecular weight increase with the flow speed increasing slowly. The reliability degree of measuring the molecular weight and molecular weight distribution is highest(95%) when the flow speed is 1.0ml/min. So, the flow speed of the mobile phase is 1.0ml/min in the experiment.[7] The temperature and solution time affect was research by comparing with the reliability degree of measuring the molecular weight and molecular weight distribution under different conditions, and we intend to optimize the experiment condition by a serial experiment. The last results show as follows: the affection of temperature and solution time is smaller for the molecular weight and molecular weight distribution., however, by comparing and analysis, we think the temperature 34℃is better and the solution time 10h is perfect.[8] The GPC-MALLS analysis shows as follows: Compared with the linear polymer PDLLA and the branched one's molecular weight versus time and molecular weight versus RMS radius plots, and the raletive of these quantities, we obtained the following equation by linear regression analysis about the EMPLA in the THF: Rw=0.608×Mw0.316,and charactered the branched structure exist or not, inferred the molecular figure of the EMPLA in the THF is sphere. We obtained the graft ratio of the branched polymer is a distance 0.72～0.82 and 0.65～0.77 by molecular weight way. at the same time, we can obtained the distribution of the graft ratio and the number of branches per molecule(0.6～1.2 and 0.5～0.8),too, these result own only by GPC-MALLS.[9] The relativity between graft ratio and cell was research by morphologic, MTT, ALP, cell cycle ways. All result shows: the EMPLA with the higher graft ratio has better biocompatibility.
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